I think Lehner will be leaky until the season ends. This is the most he's played at the NHL level in one season. He's had other seasons where's had slightly fewer minutes, but that was spread over an entire season - he's where he is now with 20% of the season remaining. Last night, he looked like Miller did when Miller was fatigued from being run into the ground by Ruff and the lack of a decent backup in some seasons.
I hope this season adjusts Lehner to the workload he'll be expected to carry as a NHL starter, and he can adapt to the workload in future seasons.