I guess I am naive---but I put a new chain on my bike and I could not believe the difference it made. A year ago when I pulled my vintage Univega out of the back of my garage to begin riding again for the first time in 15 years and 80 pounds overweight---a friend recommended that I get a new chain. I did and it immediately started skipping so I had to find a new freewheel as well. Not easy since it was a Suntour freewheel and they are out of business and no one makes them in the spacing I need---but I found one. I put on a SRAM PC-48 chain and it did fine. I put about 2000 miles on that chain. I was beginning to hear clattering/grinding "noises" especially when in one gear---but only attributed them to just having an old bike. I had the bike in the shop the other day for a new rim and had them check the chain for wear. They recommended a new chain (It was in the red). Seeing that it is so hard to find freewheels, I had them change the chain and upgraded to the SCRAM PC-58 (A whopping $7 more expensive).
What a difference! The shifting was much crisper (I am still using downtube friction shifters). The ride was quieter in all gears. It almost seemed like a different bike---all because of a new chain.
I have decided to get a chain checking tool and keep a closer watch on chain wear. I already clean and lube my chain every week or two (I'm riding around 100 miles a week). Chains are just not that expensive to replace---even the top of the line chains. Seems well worth it to me even if I had to replace them more than once a year.
This may be common knowledge and I'm just now getting a clue---but I wonder how many put up with noises and sloppy shifting when all they need is a new chain.