Squealing electric window - precursor to failure?

I couldn't find this issue doing a quick search, so here it is:

My driver side window squeals whenever it is raised or lowered. Nothing that sounds like what I heard when the backseat window regulator failed last year (no clunking or grinding sound). Is this a typical indicator of imminent failure, or is it simply due to lack of lubrication or something like that?

I'm not eager for more window repair, but with a few months of good weather left, it might be good to be proactive.

Could be either. Only way to tell is open up the door jamb and check for proper grease and/or bindng.

Be sure to disconnect battery first before disconnecting side air bag though.

Sometimes the support arm of the window regulator can bend and scrape against the glass making a squealing sound. Eventually this condition will scratch the glass. Happened to my car. I was able to reach in and bend the arm away from the glass. Not necessarily what is happening with your car. As dvsgene said, you'll have to remove the door trim panel to find out what's wrong and then repair.

Could also be the outside rubber seal.

I had a squealing front passenger window, quite loud and obnoxious. My Indy suggested a potential failing regulator. After some troubleshooting, the culprit was a rubber seal as edjack mentioned. I used RainX on the window and it cured a problem I had lived with for a couple years. The window regulator was not the issue and still works just fine.