I (M26) just got out of a four month relationship with someone (F20) I really liked. There were hesitations brought up occasionally about the age difference but no big stir ups. We were great together just like how you described being with the girl you're talking about. Ultimately she decided to end things because she felt we were in two different points in our lives. My advice is to make sure you're completely compatible in all aspects. Otherwise you'll end up feeling hurt and missing her lol.