You don't need to go crazy on the "bodywork" as it were, but do keep your drivechain clean. You'll wear through chains in particular very quickly if you leave it covered in grease and grit - this makes for a wonderful grinding paste. My winter cleaining regime is as follows:
Weekly (or maybe a bit more if the weather's been particularly grotty):
- Clean chain with Muc-Off degreaser and their chain cleaning device thingy, wipe off the excess with kitchen towel and re-lube (approximately 3 minutes)
- Clean crap out of jockey wheels (kitchen towels and degreaser) - 2 minutes.
- Check chain wear (5 seconds, plus half an hour to find the chain wear tool which invariably isn't where it should be)
- Washing up brush to get the grit off of the deraillieurs and brakes, and throw some light oil down them (not on the pads, obviously!) (approximately 2 minutes)
And after any wet ride:
- Hose down bike before putting in Garage (15-20 seconds)
As for making the rest of the bike look shiny and pretty, I only do this when I really have nothing better to do, since it usually ends up taking about 2 hours (when I do it, I go a bit overboard! Full degrease, clean and silicon spray to make it sparkle)