One should distinguish between solvent evaporation and vulcanization. If it is only evaporation, the solvent may be added and the cement can be made liquid again. However, after a number of years, this does not help and the vulcanizing fluid just turns into a ball of goo that does not react to the solvent. I.e., you cannot have a lifetime supply in practice. The lifetime is shorter for Rema.
All true!
My father-in-law used to say, "Sometimes 15 minutes in the lab will save you a week at the blackboard." Of course it takes more than 15 minutes to see how well the two adhesives work on bike tubes, but I haven't seen a difference between Slime and Rema performance. From my point of view, Slime works as well, costs half as much, and (IME) lasts at least as long in the can
and on the road.