I take at least one spare tube with me when I ride. One when commuting, and two for all-day rides. I don't patch them on-the-spot, but rather when I get home and depending on where the hole is. Two patches on one tube is my limit though.
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'75 Fuji S-10S bought new, 52k+ miles and still going!
'84 Univega Gran Tourismo
'84 Univega Viva Sport
'86 Miyata 710
'90 Schwinn Woodlands
Unknown brand MTB of questionable lineage aka 'Mutt Trail Bike'
Plus or minus a few others from time-to-time