You dont bring back up tubes to a gig, right?
Yes...I actually did keep a spare tube in my bag for each type I needed. I also carry spare power cables, spare patch cables, spare batteries, extension cords, flashlights, instrument cords (including a wireless in the event I end up having to mix FOH), chart lights, and a spare DI. That's just in my pedalboard bag. In my bass bag I have more stuff. In my "gig bag" (really a backpack) I carry power filters, power strips, gaff tape, XLR cables, extra mic (and I don't sing), and a few other things.
I also have a complete backup pedal board that I bring (my little baby board) in the event something goes south.
Now you understand why carrying a 28lb pedal board of tube gear was prohibitive. I come prepared.