How would you know if it worked?
I had slime put in some tires at the LBS when I first bought the bike (my Trek MTB). About 7 years later, admittedly after the bike had sat for at least 5 years, I tried to pump the tires with one of those old-school hand pumps like you used to clip on to your bike. I got slime all over myself. Forgot it was in there. Road the bike for another year until finally I got a blow-out -- a real one where I was pumping the tire and the tube split right at the stem.
So, maybe the slime worked because I never got a puncture. The other one is the original.