Is there a limit to the number of patches?

I've patched the front tire on my Marin Larkspur three times in the past year (hazards of city riding). Does anyone know if there's a recommendation about how many patches one tire should have? If so, I imagine it's more than three, but it got me wondering what's safe.

if they're good patches and hold air, what's to worry? if they are on top of each other, i would get nervous.