My experience in February was that the switch was gradual. I was seated at probably 11:15 or so (in a nearly empty restaurant, I'll add) and there was still breakfast food out my first pass through the buffet, along with some of the lunch stuff.
When I went back 15 minutes or so later, it was all lunch.
So if you linger during your breakfast, you'll get the chance to try some of their really good lunch stuff - think of it as a plus!
I'll also add, to clarify, that if you're late being seated, you won't be denied the chance to eat - the only thing would be if you absolutely want the breakfast foods rather than the lunch foods. (I think the latter are a lot more interesting - I absolutely love the place.)