Shedding for a few months, is that normal?

My chin Mr. B started shedding a few months ago with the visible U-shaped hairline on his back, and even a few tufts on the ears etc. It's been a few months and he still has little fur tufts on his butt/rump area. I read that shedding can take a few months or even just a few weeks, but I feel like it's been a long time?

He seems healthy/happy otherwise, doesn't seem stressed, eats regularly, and I give him a few dust baths a week. Is it normal for chins to shed for that long?