"Stretching" brass frames was a condition perpetrated by some well-meaning fool in the 60's - may have even been Val Forgett or Turner Kirkland.
When you blast away with full cylinder loads in a brass frame revolver, eventually the cylinder develops end shake (Smith & Wesson gunsmithing terminology) - where the cylinder moves forward & rearward within the frame. Immediately this looks like the frame has stretched. In reality, excess rearward recoil causes the rear of the cylinder to batter and peen the frame recess, inducing the loose cylinder condition.
Bronze frames aren't soft, they are tough, and don't stretch, but excess impact will cause damage. You can shoot a brass framed revolver for all your life, using lighter and more accurate target loads, and the cylinder will never loosen up.
If you want to blast away at maximum velocity and minimum accuracy, go buy a .357 or .44 mag. When you're done blasting & want to do some actual accurate shooting, go load up your brass-framed cap & revolver. For .36 cal (real Navy) 17 grains 3F with paper or felt wad and RB, or .44 (actually Army) 23 grains 3F with paper or felt wad, will give you optimum accuracy in either Colts or Remingtons.