Rockets can take an unexpected turn while up in the air. I am happy to report that most of my rockets caught in trees have eventually come down. One took 3 weeks. It's really not worth risking injury climbing trees to recover rockets. Do not go near power lines to recover a rocket.
Rockets are cheap to replace out of recycled materials.
In the first prototypes, there was no pop-off valves. We had a few explode, and wow, it's sounds like a stick of dynamite. To prevent explosions, I installed 150 psi valves, then 125 psi, and now we have settled with 100 psi valves. We have not have bottles rupture yet at 100 psi, and it seems to be a safe level. Even with the lower pressures, there seems to be little effect in maximum altitudes.