I could see wearing out a high performance "race" tire in 1500 miles or less, but that sounds like unreasonably little mileage from an "urban" tire. Of course, I don't know what exact tires you have (specs show your bike should have come stock w/All-Condition Sports in 32mm), your weight or the type of riding you do. Sometimes, newer riders (you?? - I don't know) react prematurely to tire wear. A bike tire can typically be ridden until the tread is very squared off, the casing begins to show through the outer rubber tread, and/or you're getting recurring flats. But, if you think the tires are that worn or you simply want something new, then replace them if you wish.

Narrower tires will require higher PSI and will wear a bit faster than wider tires of similar construction. Narrower tires are also more subject to pinch flats and offer less protection to the rim. About the only benefit for everyday recreational riders averaging mere mortal speeds is less rotating weight, something that might be noticeable on long climbs. If you're after less rolling resistance without giving up the advantages of a wider tire, look for a tire with a more supple casing and sidewall.