I have a couple of tubes salvaged, both the U ones and the spiral higher power ones, life cycle depends on flash energy and tube rating, a few 1000 flashes to a few hundred thousand or so.
If you look inside the tube there are 3 electrodes, 2 inside the glass, one of these is the anode and the other cathode, cant remember which one now but one will be larger, and have wire wrapped around it, or will be made from a tube, this gets sputtered away making it harder for the arc to jump across, increasing the drive voltage or trigger voltage might compensate for a while, but these things are a bit like crt's once they start to go game over.