Originally Posted by
Jimi77
The trails I ride are full of goat heads and slime has been great at keeping my tires full of air for a good ~20 years. I'm not sure why it doesn't work for others.

You already answered your own question, you're riding trails with a CX or MTB not with a road bike, and road bikes run 100 plus psi, Slime won't hold under that kind of pressure. WTF back at you!