Hi! We have used the pilot USPS Premium Forwarding Service on two approximately 8 week trips (from Maryland to Seattle area and from Maryland to Florida). It worked great!
We plan to use it again on our trip to Florida in Jan-Feb.
We live in a small town but they were able to set it up with no problems. They sent all of the mail each week (each Wednesday?)via priority mail and we received it in 2-3 days. On the Seattle trip, we used several post offices: picked up our mail in Ohio, Minnesota, several places in Washington state, etc. We did find that forwarding mail for pick up via general delivery at the smaller post offices in the Northwest could run a day or two over the expected 2 days so do recommend some flexibility in that regard. When that occurred, they delivered the mail to a post office further along our route at no extra charge.
As mentioned, cost is not cheap but is reasonable (enrollment $10, weekly $10.40). The USPS folks were quite helpful and using this approach avoids the problem that your temporary change in address will be interpreted as a permanent move re credit cards, etc.
Tim Stuart