Just last week I had to put a tube in the left front tire of my Cub Cadet. For 5 or more years I have been using Fix a Flat, Slime and another no-name brand flat fixer to just get by for "one more cut". Well, the leak had finally gotten so bad that I had to start parking the mower with that tire on cardboard to keep from messing up my floor. Then I had to start doubling up the cardboard and finally had to put plywood under that. When it got to the point where I couldn't finish mowing without stopping to add air, I had no choice but to remove the tire and add a tube.
What a stinking mess! I will never do that again. What should have been a 15-20 minute job took me over 3 hours (mostly because I was trying to contain the mess). I had the best luck with "Fix a Flat", and it did work well, but next time I'll just do it the correct way as it was never a permanent repair.
When it starts leaking again buy a plug kit at the flaps or Wally World. Takes less time than putting in Slime.
As I was cleaning up the mess, I was thinking that I should have done just that in the very beginning.