Summer is generally a more relaxed time for me, without regular rehearsals or frequent infusions of fresh repertoire to work on. I've been spending a lot of time lately with piano and clarinet--both old friends that I'm eagerly re-introducing into the regular practice rotation. My flute work is focused on technical study to sharpen particular aspects of my playing and prepare for whatever the 2017/2018 season might throw at me.
Some of my colleagues spend the summer in workshops or intensives to rev up for upcoming auditions and performances. If you're feeling the need to light a fire under your playing, a summer intensive can be a great way to propel yourself forward. The work to prepare for these workshops is intense in itself, not to mention the work you'll do while you're there.
Others take some time off from their usual practice routines to create some space and come back with a fresh perspective in the fall. Neither is "better." There's always a balance to be had. If you're burned out, work on practicing smarter instead of harder. Try lessons with a new teacher. Change out what material you're working on. Maybe even take some time away from your instrument (but not too long, or it can be hard to get back in the practice groove).
How are you spending the summer?