I reuse stop bath few times. I just pour it back into a bottle labeled "stop working" (funny name, I know). I discard it when it starts to change color. I do this for convenience. It works and I see no need to throw it away after session use.

Fixer, I re-use, of course. Ilford rapid fix is my favorite. I keep track of number of rolls processed and the months since mixed. Ilford says 6 months but I use it up to 9 months unless number of rolls processed gets very high. My own test showed it was quite active at 9 month point.

For developer, I use D-76. Works just fine for me. I keep them in a bunch of 8 oz bottles to minimize oxygen exposure. I use them one shot.

Something not too many people talk about.... If you use HCA to make your washing shorter, be sure to keep this in number of smaller bottles as it sucks in oxygen and deteriorates. I have seen bottles completely collapsed. I keep them in cascade of smaller bottles as I do for developers.