I employed a similiar strategy. After doing many math problems, I simply felt exhausted and only wanted to work on my verbal. So for the Manhattan online tests, I simply skipped the quant section and moved directly on the verbal. Manhattan's verbal questions are pretty decent, so I could recommend that approach if you're already solid in math and have enough quant questions for practice.
However, many will object to this course of action. You're losing six full CAT's - something to consider if you need more practice to adjust to the test environment or require extra math practice.
GMAT Club Premium Membership - big benefits and savings