chuck BFs are two main floors with a third that may contain a boss.
there are 3 Bf dungeons in act I. 6 in acts II and III.
don't know about act IV as i've not yet arrived! <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
bosses (usual quest satisfiers) can be found in any or all of the dungeons...so it could be possible to have all 5 BF quests solved in level 3 of dungeon 6.

for me, i do a 'titled' save before entering any major battle (if you know it's coming), doing any riddles, changing levels (floors, caves, etc.) or anything i know will involve quest related stuff.
i use quick saves for the in-between.
if you happen to be running off a quicksave and do something big (that you may question or wish to test outcomes), reload and put in a named save.

saves take up a lot of space, so you may not wish to keep them hanging around. there is a handy trash-can icon on the screen that allows you to discard old saves. this will 'save' you space. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />