Proof Sets are Coming
If I were going to submit some coins for grading at Economy, I would submit them sooner rather than later. I see a trend of when the US Mint releases products, the grading services get bogged down grading mass quantities from the cable networks' TV sales. This is probably what is going on now with the 2007 silver eagles. The Mint is releasing the 2007 proof sets in May and that will be another load of coins to grade. My guess is that if someone submits 1000 proof sets, they will get "Economy Priority" over your 5 coins. It is basic economics.
I would try to schedule grading away from US Mint releases if possible, or go to the Early Bird teir. It is more money if it is important for you to see your coins in less than a month or two.