Jean:
It appears to me that if you are taking the time to clean your chain every week, you are either an immaculate mechanic, or you are in love with your bike and don't want it to suffer.
For winter riding in areas where salt is used on the roads, I suggest you get a disposably cheap bike. The salt will eat your bike no matter how hard you try to keep it clean.
You will notice that most winter bike commuters ride crummy bikes - myself included. Even bikes made mostly of non-rusting alloys take terrible abuse from the salt, sand, and slush.
Check out sights like
http://www.icebike.org or even the Winter Biking forum on this site. You will find that true winter bikers goo-up every part of their bike with some kind of protective coating just to make it last through the winter.
I spray coat ALL practical surfaces (including spokes) with clear enamel. Other parts get coated with wax, grease, or oil.