It is often the moving parts (bearings, derailleurs, cables, chains, suspension components) that are ruined by winter riding. THese parts should be considered 'consumables' and you will have to replace them over time - but over much less time if you ride in the winter.

Tires, tubes, handlebar grips, brake pads are also consumables, although these are less affected by winter riding.

What I am getting at is - there is no bike that is impervious to the harshness of winter riding, and if you have an almost functioning bike, replacing or overhauling a few of the items listed above will bring the bike back to like-new function.

As for building a specific winter bike, like I said, there are parts that will always need to be replaced after a winter of riding, regardless of how carefully they are chosen. You old strategy of buying a new cheap bike for each winter is a mre resonable one, although I tend to prefer used 10-speeds converted to flat-bar hybrids... this usually costs less than $100 to get a great winter bike.

Buying a frame and building it up is a great way to spend 2X or 3X more than the cost of a bike of comparable quality, unless you have almost a complete bike's worth of compatible parts sitting in a box. If you can find a frame and all the parts used you will pay possibly a little less than what the bike would cost new, but you can buy a complete used bike for much cheaper. And no matter how you buy or build a bike, new or used, you will have to rebuild it after a winter of regular riding.

If you are in the market for a new frame, the prices start around $100 - $200 plus shipping from the mail order shops that sell them. THen you need a bottom bracket, a crank, chain, headset, handlebars, wheels (rims, hubs, and spokes), tires, pedals, cassette, brakes.... it all adds up very quickly to pass the cost of a basic bike shop bike (starting at around $300 or so), that will survive a winter of riding about the same.

In short, building from frame-up is generally not advisable. Go to a bike shop, or Kijiji and see what sort of bargains you can find.