Agreed. But how do you stop once you start???
For me what to do/not do is based on the difficulty in getting parts. The chevy stuff isn't an issue with most parts but I have another make straight 8 that is made of near unobtainium i'm going to have to live with some stuff I can't afford to fix.
I'll cut corners sometimes on things that are hidden under a dash or under the car if they are still working as intended and just clean them up. I get real picky with engines though and do the best I can... its the heart of the car afterall. Nothing finer than a good running powerplant.

PS When I was younger I used to spend summers out at my grandfathers house who restored cars. Often times he would clean parts and install them instead of making them perfect little masterpieces. It really used to drive me nuts to see him putting parts back on a car that weren't 110% perfect. It wasn't until later and I restored my own cars that I saw the wisdom... My first restoration I spent hours making everything as perfect as possible, then spent hours after it was done protecting it from damage during use. Now I practice a more mellow standard so I can drive 'em care free and enjoy. As long as everything is working great life is sweet!