Neither of us can really hope to assess the change in risk of something like DVT based on personal experience. We're talking about something that normally kills some tiny portion of travelers (1 in 100,000 passenger legs, maybe?)... if not moving around increases that risk 10x, you'd still have to do a few hundred thousand flights to know.

Edit: The annual risk of DVT apparently runs about 1 in 3,000 for the general population. So if you were a higher risk passenger (older) and flew really regularly, I could see it getting down towards say 1 in 100 annually. Even then, you'd still need decades of data to make any conclusion.