I would trim...

Looking at your pictures, your hair looks absolutely gorgeous to about the top of your hips or so (it's hard to tell in the picture).. then it gets soooo thin, and I think the "thinness" distracts the eye from the fuller section of your hair. So, I definately think that you may want to consider trimming....


...BUT VERY CONSERVATIVELY!!!! For example.. I'd probably make it a goal to get 1-2 inches cut off once every 6 months or so until the ends were nice and thick. This way, you don't lose a lot of length, but you can start working towards having fuller, healthier ends.

I know it took you soooo long to get your hair that length, so think carefully about every inch you take off... I definately wouldn't take more than an inch or two at a time... so don't let anyone pressure you to cutting more than that. But I do think that some light trimming over the next year could take your long hair from pretty.. to absolutely fabulous!!!!

HTH