IMHO, depending on how many domain classes you have, this solution can go from saving you some time to becoming a lifeguard.
In one of the projects, we started with an annotation-based ORM. We now require that the Entity class be kept as ordinary Javabeans instead of bringing any other layer-specific details into it. Therefore, we want to move to using HBM XML Method. There is an easy way to migrate.
One way to solve manual writing of all mapping files is to let Hibernate generate a database based on the actual database based on the annotated domain class Mode (I would choose a memory mode like Derby). Then, you will be able to use the Hibernate-tools plugin to generate a mapping file.
IMHO, depending on how many domain classes you have, this solves The solution can go from saving you some time to becoming a lifeguard.