Many reasons here why you need a summer bike and also a winter bike, but what it really boils down too is having a cheapish bike and an expensive bike. I ride my expensive bike regardless of the weather, as it is "my best bike" but come winter, the big problem arises of maintenance and cleaning it constantly which can be after every ride, sometimes I get home plastered in mud that farmers have left on the road and if salt has been laid and its wet, then that is more of a reason to clean your bike to prevent corrosion.
When the weather is cold and wet and and you have had a long ride, you just do not feel up to cleaning it at times, so that is where the cheaper bike comes into the equation, ride it, possibly quick wash down and relube if its lucky, but even so it also needs a good cleaning on a regular basis, my commuter never gets cleaned though apart from now and again when it gets too grimy, but it has depriciated in value over the years so its probably only worth about £50, but if i went to work on my Madone everyday, then cleaning and maintenance would become a nightmare.
) frame with steel or carbon forks - gear it with a 2:1, chainring to cog, ratio and you'll have 40, 54 and 72 gear inches. Replace any bits that are worn each Spring. Obviously needs rack and guards etc.
