Yes, but you should always have the option to break a treaty anytime you feel like it - and without any delay so you can strike when its most suitable. Sadly, most games force you to break an alliance before you can invade, which takes most of the fun of backstabbing away
I dont recall that... I'm playing alpha centauri for example, and you betray when you want. For real ou continuous time, like Paradox serie (Hoi2 being the latest), the problem is void too.
__________________
Currently playing: Dominions III, Civilization IV, Ageod American Civil War.