It converts from SSDI to SS retirement at age 65+ depending on your age.

http://www.ssa.gov/retirement/1942.html

There is a reduction in SS if taken at 62, but it would be very rare for someone to lose benefits at age 62, so unless your condition has improved there would be no reason to convert early. You'd wait for a Continuing Disability Review, unlikely to even happen btw, and once SSDI benefits were terminated you still receive 90 days transition benefits, and could apply for SS retirement at that point.

In otherwords, do nothing, and you shouldn't see a reduction in benefits. If receiving half of your spouses benefits when you turn retirement age would be more than your SSDI, you might want to look into that, but that would be rare I'd think?