I bun almost daily. Unless it is the month of my relaxer I am almost always in a bun. Even when I do a braid out, I style it into a fancier, cuter bun.
I use pins most of the time. Not bobby pins, because they cause breakage for me, or hair pins, because that is too much struggle with not enough hold. I gather my hair and twist it up onto itself, and around itself to form a roll/bun, then pin it with the duck bill pins that have the gap, because they hold more hair more gently.
I see no breakage and this is personally better for my ends than a traditional bun.
It has helped with my length and thickness, and helped me learn to not try to beat my hair into submission, but let it do what it do and help it along the way.
I also moisturize and seal beforehand, and bun my hair while we or dry. If I want more curl in it, I let it airdry and then bun. If I am going to sleep, I bun wet. I used to take it down daily to remoisturize, but now I don't and haven't for months. My hair gets dryer, but no splits or other damage.
HTH