You want permanent and no flame? Propress. The crimping tool will set you back some $$ though.

I work in an old hotel, we have a few sharkbite valves on hand for emergencies. We will solder or now Propress, a "real" valve on later.

I have never seen a sweat copper joints can fail, it's a workmanship issue for those.

I have 3" copper joints that have weeped for years, decades. Big joints are hard to heat up and solder properly. They haven't gotten worse and some day we'll shut the whole building down to fix.