There are things that add to Hashirama's Sage Mode.
.: He is under Edo Tensei, which arguably allows his chakra to never be depleted up to his threshold (remember that Edo Tensei'd characters don't gain power).
.: His kekkei genkai is Wood Style, which is symbolized to be bearers of natural energy (when you think of Natural, you think of a forest with a cool breeze, don't ya?). It's possible that his ever-present use of Wood Style allows him to tap into his Sage Mode indefinitely, even while moving!
.: His Senju descent is representative of Yang energy (or Yin? I always get them mixed up. The one about the Body), which gives him natural command of the chakra present in his body. He doesn't have as much endurance as Uzumaki, per say (although with being Edo Tensei, you can count that comparison void), but he can command a great deal more chakra than lesser clans.
This allows him to summon the correct ratio of nature energy much faster than Naruto's (add the years of mastery he must have trained to achieve) and with a longer duration.