Some vintage pen restorers have strong opinions about how far you should go when restoring writing instruments. There are those who do absolutely the bare minimum when fixing one up, only replacing enough parts to return it to a working state. Then there are those who seek out mint new parts online, replacing anything that looks too old or worn while polishing everything else until the pen in question might blind you if look at it directly!
Experienced restorers such as Deb of GoodWritersPens have Opinions about this, and for good reason. On the one hand, you might want a beautiful piece of history that is as clean and shiny as possible. On the other hand, at which point do you begin sacrificing the personality and authenticity of the pen to do this? It could be argued that it's no longer a true piece of history if you buff out every scuff and scratch that tells the story of the pen. It will look good, but if you wanted a flawless writing instrument, wouldn't you just buy a new pen?
I'm somewhere between the 'light touch' restoration approach and the 'full makeover sparkly shiny clean' one. I always want a functional pen with working innards, so I'll clean any metal parts to remove rust and replace petrified ink sacs (if the existing one is still soft and rubbery, I'll use that one). As for cosmetic treatments, I polish up any metal accents until they just begin to shine, and I usually apply a bit of silicone grease to pen barrels to remove dirt and make those look slightly glossy too. I don't make any attempt to fill in scuffs or scratches, as I feel that those are a desirable sign of age. Think about the way you'd allow a leather pen case to age -you wouldn't neglect it, you'd apply leather balm to keep it looking good,but you wouldn't freak out when it picks up scuffs. It's a natural part of the life cycle of such things.
In my opinion, it's a lot easier to remove 50 or 60 years of history than it is to re-apply it. I'm not saying that there isn't a skill to making an old pen pristine again- of course there is - but to remove all signs of age would be to remove part of its history. If you want something new and mint, there are thousands of gorgeous modern pens to choose from, so I'd always take a sympathetic approach to restorations as I feel that it yields the best results. It's largely a matter of personal taste, but I'd never want to replace so many parts of a pen that it was no longer truly original. What are your thoughts on pen restoration?