I returned to work PT - I believe it triggered a short form 455 and while I am under 20 hours a week and under 700 a month (15 hours a week - 600 a month) I just received notification that I will NOT lose my SSDI benefits.
I wanted to tell others that it probably depends on your physical scenario.

I'm 60 - on SSDI for 10 years. I was truly paranoid that I was going to lose my benefits but with my husband on the liver transplant list and ultimately almost going to lose housing I *had* to figure it out to keep a roof over our heads.
I had to.
Fortunately, I guess because of my age, because of my disability, because, because... I am OK.
thank God.
It's not easy... trust me - it's not...