As I get more familiar with quant question types, I'm beginning to see that there are only a limited number of "hard" level problems in

OG12, and also

MGMAT guides.. actually, it seems like even the MGMAT advanced problems aren't nearly as hard as the 700 level problems on their online CAT. Same is true for

GMAT club tests..

problem is, I don't want to use this limited resource as practice questions since they'll lose their meaning on second try. It feels like there is a jump in difficulty level for 700 problems, and so I find it difficult to get to that level, without using up the reserve of available problems. Any good strategies?