Although you can definately overdose on caffeine, scientists have not been able to pin any problems to long term use of caffeine.
I have seen the results of long term amphetamine use.
You really can’t compare the two.
It’s not as if all amphetamines are the same. I’m not aware of any documented evidence of long term problems resulting from use of methylphenidate (though presumably massively excessive doses could cause harm similar to caffeine). Ritalin is not meth.