I read an article about serial repitching in breweries and they repitched the same yeast for A YEAR. Their findings were that there were no significant mutations, no change in the fermentation profiles, and nothing really divergent from the original yeast genome after all that time. This was done with ale yeast pitched 98 times and lager yeast pitched 135 times, which is WAY more than people on here recommend.
I think that the biggest problem is potential infection at the homebrew scale from mishandling the yeast. To be safe, just make a starter each time.