To get fruit you need to sustain as much stalk as possible each winter. Cutting back to 18" may make an easy mulch but it sets the plant back every year. You do get freezes but obviously leave in the ground. Not sure in your zone but up here in KS zone 6 I have seen Basjoo (the usual cold hardy banana) caged for the winter and start again from it's full stalk and bloom. Caged being a wire cage filled with leaves or other mulch and tarpped. That works here, if you don't get cold enough then it might not work for you. The point being to preserve as much stalk as possible through the winter to get a head start in spring.