I posted a similar question several months back.
Having started my own restoration I am thinking part of the answer is in the marketplace.
For example, if you find an uncirculated MS-66 Morgan silver dollar that has never been touched, you don't take it out to the shop and put a buffing wheel to it unless you want to lose the collectible value (and you are nuts).
Custom car "restorers" can rip just about everything out of an old car and start over because that is what some collectors value. Beat up old cars don't bring much these days unless someone does a custom restore on them.
If you want to maintain a vintage set in a scratched up and dented condition with no thought of the set's market value, then you leave the set alone. If collectors want all the scratches, nicks, dents, and whathaveyou's then the value of set would best be maintained by doing nothing except cleaning.
Personally, I like to see the chrome glisten, the finish shine, and the set to be in as original condition as possible without all the blemishes. Conversely, I do tend to salivate at some of the recovers and restores.
From looking on ebay, it looks like some collectors go both ways on this issue of restoration. In some cases, it looks like collectors are buying the heavily blemished stuff but I am wondering if they intend to restore. In other cases, I see rather hefty prices paid for recovers and restores already done. I am surprised by the upward prices of the restores and recovers. In this case, vintage value looks like maybe it comes from eye appeal and vintage sound rather than from just the vintage sound alone.