Maybe this is faulty memory, but I seem to recall in the past that pre-release macOS or iOS versions would not update to the final "retail" release, necessitating a wipe and reinstall. That doesn't seem to be the case anymore (or for some time now).
Running betas, you'll deal with random things breaking and other annoyances, but that seems to be The Apple Experience anyway in current "final" releases. If anything, you'll get security fixes sooner (like the KLACK fixes in 11.1 and macOS 10.13.1) and do more regular testing.
Seems like an okay idea. I'd keep another device with the current public release (or earlier) for other testing.