My hair wasn't as long as yours, but I did get perms about 5 years ago. At the time, my hair was really weird, a lot curlier, with several different textures, and just a pain to deal with. My stylist (also a curly) recommended it to loosen the curl and get a more uniform curl to deal with. She has lots of curly clients, and has done it for many of them.
It worked out really well for me. It made my hair so much easier to deal with. I had a baby just before my last perm, so not sure if it was hormones or the perming or something else, but my hair ended up being looser and seems easier to deal with than it was before the perming.
Not sure if that helps, but if you stylist has done it before with good results, I wouldn't be as nervous.
3b/c normally, 3a/b in the winter