I'm in act 2 somewhere in the beginning and mostly I do side quests. Main storyline got progressed only because I didn't realize it and accidentally get into area of a quest and finish it. However lately my char begin to get dreams of pillars (of eternity I guess). So... am I on the clock? Kinda like in Agarest 2 where the more quests you do the closer you get to ending of generation. So is there some sort of a timer?

 

That kinda leads into second question - is there a free roam after beating final boss whoever that is? Or I can continue doing side quests first and occasionally return to main quests without any side effects later on?

There is no free roam after the end of the game. You need to finish all content before you jump into that magic hole, remember that.

 

As for timer: I don't think there is one. I have been sitting at 5 months ingame time and there are zero negative consequences, therefore I assume it is mostly flavor text without gameplay repercussions. 

from what I heard, once you beat the game its over

 

And there is no timer so you can complete all side quests at your leisure

Nice. Thanks for answers