I'm sure you could try to look it up— IIRC I think satellite lifespan in Project Echo was limited by drag on the balloon from a relatively low orbit, not deplet

I'm sure you could try to look it up— IIRC I think satellite lifespan in Project Echo was limited by drag on the balloon from a relatively low orbit, not depletion of sublimator. But if you're just talking about the sublimator, why wouldn't it last however long you want it to, depending on how much sublimator you put in it? Plastic's pretty airtight even if it's not perfect, and it's not like you need a ton of pressure to hold shape in a zero-g vacuum.