Have you backed up all of your current projects? Probably.
Do you save projects once they are completed? Odds are that your archiving routine is spotty or incomplete.
Right now I am rebuilding a project from six months ago because I didn't save a copy of the deliverables in a high quality format. I am getting off easy, though, because I still have all of the elements lying around- but this is forcing me to reconsider how I have been doing things in the past, and form new habits moving forward.
Could you easily recreate a project from your past if asked? I suspect the cost of a robust archive is recouped in only a few "Hey- do you still have this?" requests.
Back to my rebuild.