Once I got to about 13 weeks, my hair was very difficult to manage. Things I'd done before weren't really working. It was difficult to detangle, even with conditioner or under water. And it really didn't look good. Once I saw that, I should've just relaxed it but I pushed it to 14 weeks anyway.
My mother does my touch ups and she was having a hard time also. She told me next time I tried stretching so long I better have someone else do my hair
It really wasn't worth it.
12 weeks is good enough for me. But if it's working for you, I'd continue on. Just do what your hair tells you.