I somehow acquired all three lenses myself. I loved the 60mm so much that I considered selling the 80mm. But to make sure, I shot a few rolls with the 80mm, and realized all over again how great the 80mm is. The resale value of my 80mm is pretty low. So I decided to keep them all.

I don't regret it. I usually take the 150mm and one of the shorter lenses with me on every shoot. I use the 60mm and the 80mm about equally as normal lenses. Like you, I do use the 60mm for environmental portraits. But the 150mm is my primary portrait lens, because I find it very flattering (sometimes with tubes) for head and shoulder portraits. I find it useful for landscapes too, because of it's narrower field of view. With tubes, it's also my substitute for a macro lens.

It's interesting to see how others use the focal lengths differently. I think if I were you I'd use them for a while and see what works best for you.