When I start losing core cities I usually quit.
Falling behind in techs is not enough reason to quit for me
It is very possible to catch up even if it looks bad. It's important to establish as many contacts early on as possible so you get bonuses to research and can be more selective about whom you trade with.
same for me
I can even go on after losing one core city, but when you see a swarm (!) of cavalry moving your way and all you have is one defender per city and no way to build more than one per turn before you get swallowed by the wave, it's somehow pointless.
I'll try to find the screenshot I took in a WotM7 test game. Immortal level playing Cyrus (a WotM7 test game, using Robertthebruce's test save A, for those who want to try).
I somehow managed to give myself 3 vassals (Romans, Ottomans, Greeks), while Brennus had 2 (Catherine and Elizabeth).
It was in the rifle/cavalry era (=cossacks and redcoats era for my neighbours!).
I built up a nice stack of grenadiers and cannons, with some rare cavalries and riflemen. My units were nicely promoted (starting at 21 Xp
), so I make 2 big stacks against 2 "frontier cities" of Brennus.
Attack!
On the first turn, I take one city. The other stack moves to the second city.
On turn 2, I get next to the second, well defended, city.
On turn 3, I take this city without too many losses, but using most of my units.
On turn 4, the first city is back to brennus. I didn't even see the battles, but when I checked none of my troops of the first stack were left. All died
?
I moved my reinforcement troops towards the city and saw an infinite cavalry stack. hoho.
On turn 5, city 2 is back to brennus. None of my second stack's troops were alive. My reinforcement stack died too
On turn 6, Rome (which I captured) was starving. why?
all the tiles around it had cavalries on them.
It was like 12 tiles, with 4 or 5 cavalries on each...
rome fell of course, then my HE city got surrounded. I could draft one unit and finish another, but 2 rifles and a warrior vs 100 cavalries didn't seem fair...
That's when I quit...