I will note that Slime sells a larger jar of fluid that is labeled as "rubber cement" but has an ingredients list matching vulcanizing fluid. The smell is also consistent with that of vulcanizing fluid. I've used it with Rema patches with results identical to the Rema fluid so far. Note that the only reason I bought the Slime brand was because a friend was selling a bunch of cans at the bike swap and I just couldn't turn down the price.

Here in hot Arizona, an opened 3g, 5g, or 7g tube of fluid will usually dry up in 6-12 months if left untouched in a covered place such as a patch kit box, even with the cap screwed on tight. Unopened sealed tubes also have a history of drying up and becoming unusable in 4-7 years. You'd think this was unlikely given their sealed status, but apparently the lighter aromatic fractions can gradually pass through even "sealed" seams in the tube given enough time.