Just a quick reply here
1. NAPs will be modified in next version. It will be possible to attack units of a player you have a NAP agreement with, but not possible to attack cities or buildings.
2. Extra time is saved upon pressing end turn earlier than the expected (unmodified) end-time. Also, only gold-members save 100% (up to a maximum of 2 days / or the games standard-timeperiod). So in a game with 1 day turns, a goldmember can maximum save 24 hours (if they press end turn directly when it is their turn), and a normal user can only save a max of 25% = 6 hours.
For example, standard user A is playing a 1-day turntime game, and after 12h he presses end turn. he will then get 12*0.25=3h extra time on his next turn, i.e. 27h. So if he uses this extra time to max next turn, his two turns has taken 12 + 27 = 39 hours in total. Compared to if he wants to delay the game and always presses end turn as late as possible: 24 + 24 = 48 hours.
So there is no time added, only saved/stored to be used later on if needed. The overall gamespeed should be the same or probably a bit faster (since most players want to have some extra time saved just in case and therefore now have a reason to hit end turn asap)
I.e if a player/team wants to drag out a game, the best way is to press end turn as late as possible, and not use any extra time.