I know that midrange 30/30 loads should last at least 8-10 rounds. Between range pickup of my own and a couple of deals here I have several hundred rounds of brass so never really find out. I have reloaded some over and over when working up loads and so know they will go at least the 8-10 above. I trimmed some after about 5X I think. I think primer pockets may loosen up a bit, I have never had a head separation or split case though.
As for 45/70, my loads would mostly be light, only one I use would be midrange as I see no need. I have crunched some or damaged them in resizing, and wore out the case mouth from belling/ crimping because I use almost all cast, but again I have never had a case fail. I know many of them have been used 20 times.