I shoot a tube mag 1886 Winchester, therefore I crimp. Does it make a difference in case life? Probably, but if you shoot heavy loads, it won't matter a whit, because the loads themselves will dictate case life.
On regular loads, case life on a well costructed 45-70 can be very long, even with a crimp. I'm getting 25 loads at least.
You will get failures from crumpled brass in the press occassionally, that's probably where your most serious case issues will be. Particularly with cast bullets, if you don't own an expander like Lyman's excellent M die.
For consistent crimps, the Lee factory crimp hasn't been beaten IMO.