If Glock advises against steel-cased ammunition, they are very low key about it. I have not seen anything in any of their manuals, coursework or other printed material that makes any such statement."Shouldn't use steel cased in Glocks, harms the extractor"
If you are shooting a pre-gen4 Glock in .40S&W or .357SIG, it's a good idea to establish a regular replacement schedule for the recoil spring assembly around every 3000 rounds or so."didja know you ought to change the recoil spring in Glocks after 3000-5000 rounds"
You can get away with more rounds through the 9mm guns before they are going to need a new RSA. The pre-gen4 9mm guns would probably benefit from a new RSA every 5K rounds or so, but often people get away with going much longer than that.
Gen 4 and beyond RSAs should be replaced every 5K to 6K rounds.
It's hard to find that information, but it is discussed in the Armorer's Course.
I don't have good information on RSA replacement intervals for the slimline models, but the general rule is that the smaller and lighter the gun in a given caliber, the more often it's going to need a new RSA. So I would maybe go with something like 3K to 4K--but that's just a WAG on my part.
They kind of gave up on commonality with the Gen 5 guns because the ambidextrous slide stop made that a requirement from the beginning.Interesting then that they did dual springs for the Gen 5 when they don't make a Gen 5 in a caliber other than 9mm.
But before that, they would go for parts commonality even sometimes when it didn't make sense. The Gen4 9mm RSAs were that way. There was absolutely no need to go with the dual RSAs in the 19/17/34, but they did it anyway.