Pass Labs service is outstanding, possibly the best in the industry. I emailed Nelson a question about dimming bulbs on my SIT-2 and he shipped out replacement bulbs to me without my even asking. He even followed up to make sure I received them. I have a SIT-2 and a SIT-3 and I've owned a couple others. That J2 amp may outlive you. Enjoy.
Nelson is designing new First Watt amps, I believe SIT-4 is next up, which appears to be a reissue of the SIT-2 but with differently sourced SIT transistors.