Very nice.
So do you find that the particular manufacturing batch / reel or manufacturer of the 2n2222 used makes much difference in the performance or have you had good consistency of performance with all variants of 2n2222 which you have tried?
Do you find that the life time of the transistor at consistent performance levels is compromised at such voltages and pulse lengths and rep rates?
I've had pretty good luck with variants of 2n2222. This particular one came in one of those cheap Chinese transistor assortment packs. Occasionally you will find one that has poor risetime or self-fires at low voltage, but 95% seem to work well. For best performance tweaking of the charge voltage to just under self-fire is recommended if you desire triggered operation. If you just want the fastest risetime possible then up the voltage to self-fire level. In self-fire oscillation you get slightly better risetime due to lack of trigger feedthru adding a "foot" onto the base of the pulse. I always quote 10-90 Trise, although the 20-80 spec seems to becoming more prevalent these days.
As for lifetime, so long as the chargeline is fairly short..say under 5 meters, and the load is 50ohms you get good lifetime... I've seldom seen one of these fail in that service. If you use long chargelines, say over 100ns or drive low impedances, then the lifetime is shortened. I once built a pulser for an expermental setup that used a 2N5551 with 10 parallel 50ohm/20ns chargelines driving a 5 ohm load at 100Hz. The transistor would usually last at least an hour in this service, which was fine for the experiment. The risetime was ~5-7ns...I don't remember exactly.