I was curious about the longevity of the formula myself. I also use HC110 and it has a long shelf life.
Using Fred Pickers test method, I get full speed (400) from Tri-X 120, but only 200 from HP5 in 4x5.
I've got a batch of 510 from August 2006 that I save and run a roll through from time to time. It is all but gone. Film still looks good, but I also have some HC110 from about that same time that is still good and I've read the Rodinal users don't think Rodinal isn't even warmed up at that age.
510 Pyro being a one shot developer was one of its selling points for me. I use it in the same manner I use HC110, mix one shot, only what I need, and dump. Using two part developers isn't hard, just wasn't what I was used to.
I'm not sure how I end up with so many partial bottles, must be old age.
I generally store developer in 12 oz. brown glass bottles no matter the type, but will use plastic bottles if that's all I have.
Anyway, I probably wouldn't use a developer just because of it shelf life or lack of one. The finished product is a better gauge as to its desirability.
If you still have the 510, I wouldn't be scared of using it.
Artcraft sells the 510 kit "double" in size due to measuring ease of Phenidone at the larger quantity. I generally buy a double kit.
The single formula is
TEA 75ml
Ascorbic acid 5g
Pyrogallol 10g
Phenidone .25g
TEA to make 100ml
Granted not many use 510 Pyro, but it does let you make nice negatives.
Mike