Quad, I'll say a little about stakes, but will mostly address timing and sustainability.
I started playing in 1981. A poker pro taught me this about stakes. In a limit game, 40-60x the max bet should be the buy-in. In no-limit, 200+ the ante. He said anything less and you weren't likely to be able to play out big hands without tapping out, thus cutting your winnings if you won. He never worried about limiting losses.
I've always tried to think of games in those terms. It's probably old school, but when I hear $.25/.50, I think $500-1000 buy-in and twice that for $.50/1.00, and that's just above my budget. Maybe I need to come watch a $.25/.50 game to see how people really play because a $40/60/100 buy in seems very low to me for no limit.
There are no antes in NL poker. A $500 to $1000 buy-in is 1,000 to 2,000BB's in a .25/.50 game. $100 would give you a buy-in of 200BB's. Keep in mind, when players buy back into a cash game, their chips, unlike a tournament, have a cash value that is equal to their face value. In a cash game, stack sizes increase in relation to the blinds, whereas in a tournament, they decrease. So an 80 to a 160BB game changes significantly as the session progresses and the rebuys accumulate.
We would play four handed with $1500 to $1600 on the table towards the end of the evening.
I'm not sure this is helpful, but when I hear of cash players bailing out because of losses, I often suspect they have no real idea what their losses might be.
You can put that erroneous notion to rest. Almost every cash player knows the exact $ amount of their losses when they bust out. (You may find a drunk exception here and there, but even in those rare cases, the majority of them will know how much they lost after they sober up.)