It sometimes is the case that you can recover and re-use rail you arranged on a layout, but not often. Most often, once rail is placed, ballasted, and painted/weathered, it gets damaged when lifting it. However, most of us make determined efforts to recover turnouts for reuse since they are expensive...especially if they have worked flawlessly.
Many of us start in Code 100, but no modern railroad uses that weight of rail, and in times past, only a couple of roads used 155 pound rail, one being the Pennsy. Code 100 works out to 165 pound weight...grossly oversized. So, by the time we're thinking of starting a second stab at a layout, we often resort to a better fit, and that is either Code 83 or even Code 70. That means we won't even re-use our Code 100 turnouts because they'll look bulky next to our bran' spankin' new Code 83. What a shame. Or, you could opt early to use Code 83 and preclude having to place all the Code 100 stuff, including turnouts, in the trash. If you recover most of your Code 83 turnouts for Round Three, you'll save a hockey sock of money.