I've had good success in the past with dry hopping as you described. I regularly dry hop in this way except I now use a large tea ball instead of the hop bag. In any case it works fine and just remove when the flavor is the way you want it, I wouldn't have a set time like "a week" for instance. Also, after removing the hops and drinking more of the beer, you can repeat the process as the hop flavor/aroma subsides. Cheers!