The evaluation isn't really looking at "you," it is assessing your situation!. If you win $1,000,000 in the lottery in this period of time, guess what, the SSDI won't be "needed" anymore :-) Maybe you'll find a wealthy partner to marry who wants to shower you with all good things, make you a true joint heir to all they have (my husband and I own all our property jointly, so if he dies, I'm the "other" owner so it just stays with me and vice versa) maybe you'll discover a job/avocation you can do from home that makes good money or maybe you'll write a book about your condition, Oprah reviews it and you become an overnight wealthy author (look at J.K. Rowling's/Harry Potter's author's life), LOL; lots of things can happen in a year and a half.

However, if none of those things happen, if you are still roughly in the situation you find yourself in today (no old maid aunt dying and leaving you her home and money for its upkeep? -- I had a friend of my stepmother's whom I knew as "Aunt Martha" die and leave me $10,000 I wasn't expecting!) then nothing will change, they'll just renew it.

SSDI is based on your or someone immediately related to you's (parent/spouse) work earnings! It's not a "gift", someone paid into the system and now you get money out for that payment. But you only get it if you need it; unlike Social Security itself, if you don't need it, you wait until the proper "age" and receive your Social Security then (I'm 62 and got my first SS payment the day after Christmas :-) Usually though, disabled people can't wait until they're "retired" because they have become or have "always" been disabled.