Carb Fuel Evaporation?

Some times after only a week I need to crank for almost 30 seconds or more. My garage is usually around 45 to 50 degrees in the winter. I have this problem even in the summer. There are several real gas locations in my area. As far as I know the starter in my car is original and I don't want to over work it. The car has 10003 original miles.