I don't really see how locking someone up to an 8 year deal protects you if you're concerned that he might not pan out. The opposite can occur where you lock him up at the rate you want, and then he turns into Andrew Raycroft.
Sure, but you're also not paying him based entirely on what he delivered last season.
Length vs. AAV is the eternal compromise.
He's not going to get Vasilevsky dollars on an 8 year contract even if he played as well as him last season. Not enough experience.
If he plays like a 10 or 11 million dollar goalie over the life of his contract, well, the gamble pays off. If he doesn't, then it didn't.
Boston wants to gamble on the long-term contract because they -do- believe they have a #1 goalie and by locking him up now, they'll save money on the cap later. Savings that could be vital later on.
Swayman's agent knows this and is holding out for more.