[MadMax]

It's a bit hard to say. Some GBBs have chronic issues with propane. For instance the slides for TM M9 and M9 variants (Tac Master etc) are known to eventually fail under propane. Western Arms heavy weight slides eventually crack, but for some reason their chrome plated 0.45 slides seem to be really durable. I suspect that the chrome plating prevents WA from adding metal powder fillers (to increase weight) because they interfere from the chrome plating. Because of this, you can have more plastic chains entangled with each other instead of fewer wrapped around sharp poorly bonded metal bits. I have never heard of a 3.9" full auto Prokiller (lightweight slide) or any chrome plated (mirror shiny not satin shiny) slides breaking from propane.

There's also the TM Hicapa build which has been out for more than a year with no slide failures not due to drop impact.

In short, you have to be more specific in your question as various models weather propane differently. Try asking: "Do you have a INSERT GBB MODEL and how long have you used it before the slide broke?" kind of question. Otherwise you get a mess of generalized observations mostly about GBBs you may not be interested in.