I'd agree that you should definitely avoid too-small or micro braids, which can really screw up your hairline. If your hair is already thinning, I'd slather on the Surge, or ORS Temple Balm, or whatever you find that works best for you.
I wore box braids for years, back to back, with very few breaks in between. They were always about the size of a pencil. Thankfully, I had no damage or thinning to my edges. As Shatani says, it can be done.
In addition to braiders pulling too tightly on the edges, you can also lose hair during the take down if you're not super super careful, especially around the fragile edges. Don't discount the benefits of a good daily scalp massage too, to get the oils and the circulation going. Good luck.