There isn't a point of no return between A1 and A2. Rather, you need to do certain A1 events prior to A2 or those events resolve without you (e.g. Goblin Attack, several others).
You can travel back to A1 while in A2. Only A3 prevents back-travel, and that's for well-established story reasons.
I generally prefer having control of the timing rather than having it being tied to X amount of rests or something (notable exceptions for certain quests existing, of course).
BG2 and ToB both had notable points of no return. Paying the fee in Athkatla to recruit allies is one, any time you ever travel with Saemon is one, leaving the besieged city is one in TOB, etc. There were also a number of time-dependent quests, most notably those involving a certain dragon/drow situation.