I'm a little nuts about bike love but I think it's time well spent. Familiarity with your machine will allow you to spot potential problems before they become disasters. I rode all the H2H races this season, the DH 40, and countless miles either training or just for fun. I didn't have any mechanical problems. Just the other day while cleaning my bike, i noticed a link was not folding properly. upon further exam, I decided to replace my chain. I'm a 180 lb rider and I've been known to put some torque on components. I ride a 3X9 full squish 29er.
wipe down a dirty frame and wheels with "wet wipes". remove the moisture residue and any lingering dirt with a soft shop towel.
Drive train, gets a series of brushes, the best I've found is from Spin Doctor. the bristles are long and stiff enough to get between all the rings (front and rear).
Chain- stiff brush, best applied on the chain in between the rear derail pulleys. you can hit all 4 sides of the chain without the wheel on and still have ample tension to use the cranks to spin it thru.
nooks and crannys- i use a toothbrushes, rags, and my personal favorite...an air compressor. Never water. NEVER WATER! and if I'm still interested after all that, I'll hit the frame with a waterless shine polish. The entire process can take less than hour or as many as 3. it depends on how many beers I plan on drinking.
Keep it clean, it'll work when you need it.
I always check each spoke and nipple and I try to remember to check each bolt and bushing while I'm doing this.