Guidelines would suggest min 3 months on blood thinners.......but they'll have to screen potential causes and he'll have to hope he doesn't have complications. At the very least, this will affect his off-season again which sucks. It's possible he'll miss the early start of next season, and if he has another clot, it's possible that he won't be able to play again (lifelong blood thinners).
Here's the other kicker though.......these are serious in that they can travel up to the lungs. Those that get DVTs have a high risk of getting another one with the same risk factors at play. So......if I'm Brock or the person giving him advice, I think I'd be focusing on the amount of travel which has to be the #1 modifiable risk factor. The Canucks have the most travel in the league. I hate to say it, but a trade to a New York team would probably be in the best medical / career duration interest for Boeser. A big loss to the Canucks, but a trade early in the next season would probably be a smart move.