Winter is hard on my drivetrain. (You're all familiar, I'm sure. In the world of bicycles, the drivetrain consists of a series of cogged wheels at the pedal end, and the rear wheel end, and a chain that connects them. Elegant simplicity!)
For one thing, I'm not very faithful about cleaning and lubing my chain. Especially the cleaning part.
For another thing, water, and dirt, sand, grit, etc., are not friendly to moving metal mechanisms.
Combine all those bad elements, and I have to replace my chain, and my rear "cassette," about once a year. (Some would argue that it should be done more often... but my motto is, "if it ain't broke, don't fix it." Realizing that I run the risk of ending up with it "broke" someplace a long walk from help. So far I've been lucky in that regard.)
A couple winters ago, I'm embarrassed to admit, I let my chain get so worn out that one of the side-plates (the link things that form the long part of the chain) was all the way worn through. So it was only connected on one side. (I hope I'm adequately describing the situation.) And - after I discovered it, I probably rode another 150 or 200 miles! (Being VERY aware, of course, that I couldn't be accelerating through an intersection with oncoming traffic, or some other situation where my life or safety depended on chain-integrity.)
My chain is starting to skip when I put the hammer down. It's worn out, and my most heavily-used rear cogs have been worn from jagged peaks down to foothills. If I can make it for another month, I'll be happy. By then, most of the sand will have been swept off the local roads (hopefully), and the rain might be tapering off.
The whole operation costs maybe $40. $15 for a chain, and $25 for a cassette. And an hour or so. And a willingness to get my fingers greasy. (That's always some nasty, dirty grease, that takes 2 or 3 days before it all washes off. I oughtta try some dishwashing gloves sometime.) I've got maybe $20 worth of semi-specialized tools that make the job much easier.
It amazes me that some cyclists (including cyclists who look like they should know better - at least, they are astride some sweet, expensive bikes) don't seem to understand that a chain needs some maintenance. Criminey! You can hear 'em squeakin' 2 blocks away! (Way back when, I wrote about it. "Johnny Oilcan." Click HERE to read.) Of course, the reality is, most of those department-store bikes are worn out about the same time as the chain is. So the whole thing goes to the landfill.
Bicycle Guru Sheldon Brown has written some great advice about maintaining that drivetrain. You can read his practical stuff HERE.