The old timer knew what he was doing. He assumed you were not going to take the scope off and on. Depending on the scope and the mount, the zero's are stable. I regularly remove the Redfield 3200's, and Lyman Super Scope on my target 22lr's. Pictured is my Rem M37 with a Lyman Super Scope.
The barrel dovetail system and scope mounts are extremely repeatable. I do have to make elevation and windage adjustments, which is why you get sighter shots, but my zeros are all different at every range for elevation, by a couple of clicks, and windage zero depends on the wind.
Pictinny rail mounts are very repeatable with a good scope. This monster scope comes off the rifle and goes into a different safe. Shoots close enough on re installation that only a click or two is needed in the sighting period.
Now with sporter scopes, you take the things off their mounts, depending on the mount, it may line up straight or not. I never had a scope line up the same with Redfield mounts, Always had to go back to the range, shoot the thing, to establish a new zero if I took the scope off. This rifle has an antique Weaver 4X, I am afraid to make any changes when shooting for group size, as with a sporter scope, the group may move, or not move, or won't move till two shots later. The things may crazy move where you get a bullet way the heck out. This group is low and left, but that is OK, the rifle shot a 5 3/4" 17 shot group at 300 yards. I did mark the 100, 200 and 300 yard settings on the turret.
This rifle, also a 30-06, but with a 6X Burris sporter scope
I established a good 300 yard zero back in Feb and I marked the 100, 200, and 300 elevations on the turret. You can see the white fingernail polish on the top and side of the tube.
Just shot it last week, using the markings for my 300 yard zero, and this was the first shot, cold bore zero at 300 yards, after examining the wind drift through my spotting scope. It was so pretty I had to take a picture:
So heck yes, keeping recordings, marking the scope, or the stock, is very important if you expect to be in the center. Also is very important is knowing your equipment. Does your scope line up again after taking it off? Are elevation and windage changes repeatable? Or does the scope give a crazy point of impact after an adjustment? Only way to know this is by shooting the things, not reading the opinions of internet keyboard commandos.