Get RID of the Behr! My 4-year old is a Home Depot Shareholder and I say get something that's good. Steve's recommendations are the same as mine. If you want a deck that looks good AND lasts, spend some $$$. I used Behr before I knew how bad it was. It's coverage is lousy and it's hard to get off. I'm still trying after 4 years!!! I'll never stain it again. Next time, I'll use a clear sealant.
Remember, as Ma Bell use to say, "You get what you pay for." My best to ya and hope this helps.