At What Point is the Needle Damaging Records?


I have used my Denon 110 between 1-5 hours a day for the past three and a half years, and lately I noticed the highs are beginning to sound a little muted. Could I damage my records by not replacing the cartridge right away?
jmoog08
It may not be stylus wear but rather the suspension giving way. I don't know how to check that, but I agree with Stew, check the VTF/VTA first.
Get a loupe or magnifier and carefully examine the stylus. Sometimes you'll find dirt is the issue. A layer of grunge may have built up that does not come off with normal light brushing.

It may be difficult for an untrained eye to spot mild wear, but it's still a pretty good habit to visually check the stylus periodically.
Ask yourself which is less expensive, replacing your cartridge or replacing your record collection. I think you know the answer. You asked if you might damage your records by not replacing the cartridge now. You described the sound you are beginning to hear. Do you really need a second opinion?
That's quite a few hours, I agree you may need a replacement. As mentioned check your set-up and try this cheap method to clean it; http://www.high-endaudio.com/Magic.html