Re: Extremely long waits between turns
The main culprit for slow end turn times is scripts. Trying to run the game on an old computer will also obviously make the game run slow. What are your system specs? And, do you have any submods? Many large submods add lots of extra scripts that can really slow down the turn time. If you have extra submods you might just want to go back to vanilla TATW 3.1. If you don't have any submods you can still try deleting some scripts.
Take a look at the campaign script file and see what you can live without.
Medieval II Total War\mods\Third_Age_3\data\world\maps\campaign\imperial_campaign\campaign_script
When you find a script you'd like to delete highlight the lines and delete it. For example, if you'd like to delete the garrison script find the line that says:
;#################### Garrison Script Version 3.0 #####################
Remove everything below it until you find the line that says
;########################### MONEY SCRIPT ##############################
For more information you can see look here and here.