I think he means it's mental to imagine Christians actually doing that. I agree.
No judgement in if you do that, good for you. However the point is not that it's too much reading or w/e, but rather that it's far more than the typical christian cares to do. To assume christians actually do that is the mental part, but you choosing to do; if that makes sense.
edit: To the downvote, do you honestly think the majority of christians in America, some self proclaimed 70% of Americans iirc, read several passages a day? Really?