I noticed over the course of many months that during payment time the Canadian dollar gains 3 - 5 cents on the US dollar and here is my theory: Just before PIP the US dollar was worth about $1.26 this month, but once it started, over the course of a few days the US dollar dropped to $1.23, possibly due to Google buying mass amounts of canadian dollars to do thier payments, so here's how you can benefit. The first payments that go out are WU and check, so with this payment method you are getting the best exchange rate, but EFT starts usually a couple of days later, after a drop in exchange rates, so accoring to my theory by selecting check over EFT you should make about 3% more. Thoughts?
A 4 month trend graph is here: http://www.x-rates.com/d/CAD/USD/graph120.html I don't see any 'Google effect' and doubt that Google makes enough Adsense payments to make difference. In any case it would be offset by Adwords revenue going the other way. I wouldn't try to play the exchange rate game, it's too risky for the potential gain, just settle on a convenient payment method for you & stick with it.