Is tube popping an indication that they need to be replaced?

I just replaced the power tubes in my 2 channel dual rectifier. This is the first time I've handled/replaced tubes. I replaced them brecause I thought that 6L6s would suit my style more than the EL34s that were in there, in addition t the fact that I haven't changed the tubes since I bought this amp used. It was a somewhat dusty Rev G I saw at the music shop in town for $999 (good deal?). I love this amp, by the way. What I noticed, however, was that every time I switched the amp on from standby, and vice-versa, it made a somewhat loud popping/cracking noise... maybe even a snap.. I took this as normal. Since I have changed the tubes, the sound ceases to exist! Now I know I couldn't have been playing with blown tubes because the amp still roared, so is that popping/crackle sound an indication that the tubes are on the brink of death? or is it common for EL34s, since they run hotter, to make noise compared to 6L6s? Both tubes in question are Mesa branded (JJs I think).

Cheers.

Crackling is typically a sound associated with failing preamp tubes - Popping is often an indicator of a failing power tube. Many people describe their amp popping in the days/weeks/months leading up to power tube failure. Glad you got it sorted out first!

sometimes a bad cap will cause popping as well