Yes, since he can spend his mana more efficiently during low damage periods than you can. Then he can chill out a bit when you go ham and burst.
What other advice is there to give? If you run out of mana you've used too much mana, period. If you want more mana then use less mana when you don't need too. Endlessly spamming smite will oom you, so sometimes you just wanna chill for a bit, there is plenty of times where there is time for one healer to chill and not heal.