Yes, of course it can work if you know...it works!...even good things don't work out sometimes for one reason or another.
Have you talked to him about what to do if he wants to date somebody local if it turns out he has to stay long distance longer than you expect he might? Do both you and your husband want to be poly-fi? One of the things I see blow up triads most would be eventually one or two of the group wanting to date outside after originally agreeing they wouldn't, not really looking down the road.
I'd go from the assumption that regardless of how you feel right this moment, everybody will want to date others down the road, being prepared for that is a lot better than being blindsided by it someday.
Of course if you all want to move in together, there's lots of good threads on all the complications that come along with that, as well as the general recommendation to not move in together until you've been involved at least a year, and whatnot.
Happiness will never come to those who fail to appreciate what they already have.