Originally thought it was strange to sign a 10 year deal, as Arsenal have shown it can soon leave you miles behind once other sides get renewals every 3,4,5 years.
But then it's obvious, if you're the United board and know you're in with a good chance of being in the wilderness for a while then securing as long a deal as you can makes perfect sense.
United have set a bench mark so similar sized clubs (Madrid, Bayern, Barca, us, etc) will secure a similar level upon next renewal, although I'd hazard a guess none will be on such a long term contract as will know they can increase it again on the next renewal.