I think that the number, 85 techs is enough, or CAN be so.
All depends on balancing.
I think the tree is very important part of the gameplay,
Soren called it "the backbone".
The tree should be kind of ready by now, how can you test a game(play)
without a proper tech-tree? And in the summer beta testing begins.
On the part-tree I gathered, there are 38 techs.
One can wonder the possibilities:
1.
Wow, you can rush to THEOLOGY in
4(!) techs:
Mysticism - Plytheism/Medtitation - Monotheism - Theology.
Yeah, becoming a religious superpower of the world!
But oh, just where is my military to support me???
Ok, lets get some miitary AND religious power (Theology):
This means to add 2 (Bronze W.) or 3 (up to Iron W.) techs,
this means
7 techs.
Oups, but then I just stuck with the basic Civics???
No, I need at least Monarchy...
That means again 1 plus tech - but the best would be
to get Civil Service, so not 1 but 3 plus techs:
10 techs in total...
But then, what about diplomatic possibilities...?
I guess I would need Writing and later Code of Laws... errr...
2.
Let's get brutal and be military might!

:
I want archers, horses, spears, swords, some catapults...
To get them all, I need
Hunting, Archery, Bronze W., Iron W., Machinery...
a total of
7 techs.
Again, I definitely want some better government...
to get Civil Service and Monarchy: plus 6 techs,
a total of
13 techs(!)
* * *
The above thoughts are just experimentaing,
but I think this tree-structure can work...
I hope they will TEST it all the way down and up
for BALANCE...