I think I'm up to six on one of the errand bike's Schrader tubes. I'll keep patching until it's more patch than tube. But I haven't had any puncture flats since switching to Michelin Protek Cross Max tires. Bulletproof.
For my road bikes I use Lezyne self-sticking patches, which are nearly paper thin. They don't interfere with seating tires on tight fitting rims. I may have three patches on one tube.