Dear friends, please tell me what is the maximum size of *.png files that one can render in Apo 7X with flam3 engine and how to make it larger?

Sometimes I "ask" it to make a rather big file (>20 mpix) and after say 20 - 30 hrs of rendering I have a *.bmp with its poor quality and inability to be postprocessed for print. I want to know the maximum possible size (Mpix or MB) of *.PNG beforehand.

Or does it depend on the PC configuration (say, amount of RAM)?

Or does it depend on Apo version one uses (I use 3Dhack, 2.09 & 7x v.15)?

Thank You in advance,
Anthony.