Throughout Kevin Durant's free agency saga, most analysts agree that the smart move for Durant would be to sign a two-year deal, with a player option on the second year (AKA a "one-and-one" deal). By signing a deal like that, Durant could opt out next season and sign a bigger five-year max contract than he would if he signed a five year max this summer.
Why? Because max contracts are determined by a percentage of the cap in the season they sign, and since the cap is expected to go up another $15-20 million next season, Durant would get a share of a bigger pie next summer.