It would have taken them anywhere between 4-6 weeks to occupy all of Bohemia and Moravia - possibly longer.
I think that - with some luck - they could have resisted longer than 4-6 weeks.
We should note that the German army in 1938 was much weaker than one year later. On the other hand, Czechoslovakian army was of similar strength as the Polish army one year later, if not stronger.
However, indeed Czechoslovakian generals were exactly as pessimistic as you are.
According to this article:
http://phw.org.pl/historia-wojskowo...zanse-czechoslowacji-w-wojnie-z-niemcami.html
Translated excerpt:
"In case of lack of French military help, Czechoslovakian staff officers did not see any chances for successful defence of the country."
Well, this is why they decided not to resist the German invasion after the Munich betrayal.
But - in my opinion (and numbers also indicate this) - they still had a better chance to resist than Poland one year later.
The article also says that the Czech defensive plan against Germany (cryptonym "Variant XIII") was pretty similar to the Polish defensive plan "West" in 1939. They also assumed gradual withdrawal from the west towards the east and delaying combats along subsequent lines of defence (Veltava River, Czech-Moravian Highlands, Motlava River and in the end mountains of Javornikov and White and Small Carpathian Mountains as the final bastions of defence). The main premise of "Variant XIII" was to survive until the main French offensive in the Rheinland is launched.
One of the key elements for this plan to succeed, was firm defence of Northern and Southern Moravia (in order to prevent the rest of Czech forces from being cut off and encircled by German attacks from the north and from the south aimed at cutting Czechoslovakia in half). This is also similar to the Polish plan "West", one of the key elements of which was firm defence of Silesia, which was to be the solid "hinge" for the "door" of maneuver (while along the rest of the Polish frontline - the "door" - gradual withdrawal was planned - exactly as in the Czechoslovakian plan).
When it comes to the German "Fall Grun" plan - its main premise was a strong attack against Northern and Southern Moravia in order to cut Czechoslovakia in half (cut off western regions from Slovakia) and thus trap Czechoslovakian forces defending western regions (Czechia and Moravia) in a huge pocket, preventing their withdrawal to the east. This is also pretty similar to "Fall Weiss" plan of the invasion of Poland.
Both armies (German and Czechoslovakian) were quite mobilized and ready for war in October 1938 - here is the deployment of forces on the eve of the planned German invasion of Czechoslovakia (please note that Germans deployed only 44 divisions in the first attack wave - not including reserves -, which is a considerably smaller number than deployed initially - not including reserves - against Poland in September 1939):
Black - German forces
Red - Czechoslovakian forces
Here apparently some alternative version of the plan (but pretty similar, apart from a few exceptions):
http://phw.org.pl/historia-wojskowo...zanse-czechoslowacji-w-wojnie-z-niemcami.html
And regarding the probable Polish-Czechoslovakian alliance against Germany (which in the end did not take place):
A translated excerpt from this article:
http://forteca.w.activ.pl/zaolzie.html
"... When President Moscicki asked President Benes, if Czechoslovakia was going to defend [against a German invasion - Domen], with addition, that if it is the case, then Poland would support Czechoslovakia, Benes replied after several days, that Czechoslovakia had no chances for successful defence and that it would fight only in case of France ensuring her to provide support, underlining that Czechoslovakia would not undertake military initiative on her own. In Warsaw this response was recognized as a response agreed with the Soviet Union... "
A decision of war against Germany in defence of Czechoslovakia undertaken by authorities in Paris would automatically mean accomplishment of Polish-French alliance against Germany (and if France supports Czechoslovakia against Germany, then Poland - a country which has an anti-German alliance signed with France - also must support Czechoslovakia, French ally).
So if France supports Czechoslovakia, then Poland is also obliged to do this - due to French-Polish anti-German military alliance.
Polish government was ready for this possibility, and was ready to join a war against Germany in such case. But in the same time the Polish government did not believe that such a course of events can happen, because it rightfully evaluated French intentions to "preserve peace at any price".
France did not support Czechoslovakia, instead France and Britain betrayed Czechoslovakia at Munich. In such case, Czechoslovakia did not have any intentions to fight without French support (even with Polish support).
Munich Agreement is also one of reasons why Hitler decided to invade Poland later.
At Munich Hitler realized that he had a chance to built his position basing on cooperation with the Western Allies (like in case of the Munich Agreement), instead of basing on cooperation with Poland and on friendly neutrality with Hungary and the Soviet Union.
Hitler became confident that Western Allies were going to give him anything he wanted, as a price for preserving peace in Europe.
That's why Hitler was surprised when France and Britain started to support Poland when he demanded the return of Danzig to Germany.
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So, to summ up in several points:
1) According to Czech generals, they had no chance to resist. According to Czechs, they only had a chance with French support.
2) Czech government did not want to fight without French support - and Polish offers could not convince them to change their decision.
3) There was also the issue of Soviet support for Czechs - but Poland would never agree to pass Soviet forces through her territory.
4) Poland had better relations with Germany (but no alliance - as some people wrongly indicate) than with the Soviet Union at that time.
Regarding the Polish taking of Zaolzie (region with ethnic Polish majority) as the result of the fact that Czechs entirely gave up their fight:
1) That occupation of Zaolzie was not agreed with Germany, as some people claim - it was a bilateral Polish-Czech matter.
2) Hungary also did not have any alliance with Germany, even though it also annexed parts of Czechoslovakia to its own advantage.
This was a mistake. Czechoslovakia in 1938 had a better chance of resisting a German invasion for long time than Poland had in 1939. The German army in 1938 was not yet as strong as in 1939, while Czechoslovakia had a much more favourable geopolitical situation (shorter borders, mountains, stronger fortifications, etc.) than Poland and also it had an army of similar strength (or even stronger) as (than) Poland one year later.
Czechoslovakia also had strong war industry, largely capable of replacing wartime casualties in equipment and ammo expenditure.
One factor which worked against Czechoslovakia were large ethnic minorities, more hostile than minorities in Poland.
The "5th Column" in the Invasion of Czechoslovakia would thus play an even bigger role than it played in Poland.
