Off the top of my head I see at least four contributing factors to a player staying healthy.
1) How recklessly they play the game. Beyond just how physical they are, I also think of this in terms of how often a player takes risks by going to the front of the net, or holding on to the puck a second too long to open up a passing lane, or continuing to accelerate through the neutral zone despite the fact they've bobbled the puck and have their head down, etc.
I think Lindros is a classic example of a guy that was very reckless, on both counts. When he was the hammer he was often throwing his body around with little attention paid to exactly how he was making contact. And on the other side it was the nail far too often because he either didn't care to ease off when he had his head down, or never learnt how at the lower levels because his opposition was never really large enough to actually hurt him.
I think in today's NHL there's a lot of bangers that are good examples, Tanner Glass, Colin Fraser, Jared Boll. Guys that know that they're not in the NHL if they're not being somewhat reckless with their bodies. On the other side I think guys like David Krejci and Ales Hemsky are good examples of guys that are reckless by just how often they misanticipate a play or hang onto the puck too long.
2) How good a player is at deterring the opposition from playing recklessly (or dirty) against them. Never saw Gordie Howe play, but by all accounts he was a master at this. You may catch him with is head down occasionally, or have an opportunity to really stick it to him but you knew you'd better knock him out of the game or he was going to do a lot worse to you later.
A player that I have seen play that I'd put in this group is Mark Messier. Mess was forever the guy that would bring a knife to a fist fight and then grab a gun after you found a knife. There wasn't really anything that you could do to him that he could figure out a way to do 10 times worse to you in return.
Today there's some that get a bit of extra space and respect, but you can get away with the shear violence you used to. I will say it isn't very often you see someone take a really run at Chara though.
The last to are pretty self explanatory.
3) Ability to heal quickly. I think in this case it has a lot to do with just how focused a player is on the fact that hockey is their job. How well they can stay on a diet, how strictly they follow their recovery exercise regimen, stuff like that.
4) Ability to withstand pain.