I mixed a batch of JOBO/Tetenal/Unicolor 1L dev, blix and stabilizer in January. I developed 24 rolls from then until last week (four months total, kept in cold storage when not in use) when the developer finally became exhausted (luckily I clip tested so as not to ruin film). I mixed up a new batch and am already 4 rolls of Ektar 120 into it, works great but you MUST re-use it to get more than about 4 rolls developed in 1L.
What kind of spotting are you getting, can you post a sample? Could your water be too hot? I used hot water, around 50C on one roll early on and it had red spots from the emulsion being overcooked. Keep it to at most 40C as per the instructions and it should be OK. Or are you getting milky white spots from the stabilizer/drying aid?