In my experiennce, after some point of time, we need to be versatile! Be jsut open to any technology, learn the fundamentals of what you're working on and build the path on it.
It would be an opinionated answer to say that one must work with Spring, Hibernate based development project. A maintanance project doesn't stop you from sharpening your learning! Development & Maintanance, both will teach you different ball games altogether! At the end of the day, it is upto you to choose to learn or not!
Good luck!