Threads stretching is how it’s supposed to work. Note that there’s a difference between elastic deformation (springs back) and plastic deformation (doesn’t spring back).
If your threads are stretching so much that they’re plastically deforming and impacting timing, you’re torquing the muzzle devices on way too tight. If you’re torquing it to recommended spec, you should be well within the elastic limit of the threads and it’ll time the same every time. You can even use timing to get your torque into an acceptable range.
Note that there are exceptions to this in weight-sensitive industries - auto/aerospace, mostly - where bolts etc are loaded to the hairy edge, but firearms are almost universally designed with massive safety factors on everything.