How long are people with deep vein thrombosis (dvt) likely to live?

Quite Variable! Since many things can contribute to dvts in the leg (see other posts), the life expectancy can be essentially normal, to quite reduced. It really depends on what, if anything, led to that person to have a clot.
Determine cause DVT. While a DVT can be fatal, more often than not, one must be diligent about evaluating the cause of the DVT to prevent recurrence or as a symptom of a more serious underlying disorder that could effect your morbidity or mortality.
No difference. Dvt does not really change how long a person lives unless a complication occurs like pulmonary embolism. This usually occurs early after symptoms and the chance of this is less with blood thinner treatment. This is why it is important to see a physician for leg swelling and calf pain.