In the winter I usually only clean it when it gets really mucked up (slush in rear cassette/frame/derailleur pulleys). I need to learn to lube the chain more often as well - that helps out a lot with keeping things running smoothly. In the summer I think it's probably a good idea to clean your bike after every few weeks just to make sure things last - the dirt buildup on the chain can eventually get really hard to get off if you leave it for too long. Your gears can wear out quite quickly too, especially if you continue with your mileage. I started having issues with shifting gears around the end of last winter with gears skipping randomly while riding and not shifting when I used the shifter (more frustrating ****ing thing ever) and I think it had to do with the wear on the bike.
For sprints I usually start in an easy gear and work my way up to the highest one. I have no idea if that's proper technique or whatever, but it's always worked for me. I usually am in the highest gear in no time though and in an upright position, in the drops of my handlebars in the midst of the sprint. My portion of my rides where I sprint is down a long road right after a right turn though, so I guess I kind of have to start in an easier gear after the turn. 48kmh is pretty awesome though. I can usually only hit 40 (but then again more then half of the time I have a damn headwind in my face in the summer months
![rant :rant: :rant:](/styles/default/xenforo/smilies/rant.gif)
). With no wind I can get close to 50. Tailwinds though are a different kind of fun.