Your question is unanswerable, because you haven't specified how large your tolerance is. A 2.5% AM-2201 blend is a really strong blend, and will own an inexperienced user in 1 hit - so that's about the strength of the strongest herbal blends you've probably been using. JWH-081 is about 20% weaker by weight.
However, when you get to the point where even high-potency herbal blends aren't getting you high, you need to take a break, and bring your tolerance down.
There are plenty of records of people smoking little (and not so little) piles of pure JWH-xxx or AM-2201 - highest i've seen was taking doses of about 100x what a non-tolerant user would take, and not getting good effects. The problem is that, unlike plain old weed, synthetics can raise your cannabinoid tolerance much higher, and you can get non-trivial sideffects and experience withdrawal (if you care to do some digging, you can find a few reports with specifics - symptoms seem to vary). You don't want to get to that point, and increasing the dose until you get a decent high, as you've stated you plan to do, is going to get you to that point.
You should cut way back - reduce how many times per day you smoke, ex, smoke only at night, or something - or quit entirely and take a decent break from cannabinoids.