Slime is what I am using currently to patch tubes, IME such cans are good for about 5 yrs before evaporation thickens the
goop to the point of unusable. At $6-8/can I would throw it out but I haven't bought one in a while and note they are upto
$10-12 now. Slime is not 'vulcanizing' ie chemically reactive with the patch, which gives a somewhat superior bond to
such as slime, but IME slime or its analogues are adequate. Vulcanizing cement costs ~3x as much. If you patch a lot
Rema patches are on amazon in boxes of 100 for ~$20 or so.