My dad has recently stopped collecting. He had been collecting US, singles and plateblocks. He has a large accumulation of surplus postage from the last 10 years or so. Right now, his plan is to use these as postage. Are there any of the recent issues that would be worth more than that? He mentioned having a bunch of stamps with high denominations (express mail, priority mail, etc). He is not necessarily looking to sell anything as discount postage, but if there anything that he should look to separate out and not use as postage? Most of these were bought either at the post office or via mail order direct from the post office. Thanks.
Check ebay for current sell prices on priority/express high value stamps. I see some of the older unused MNH issues getting more than face. So it might be a good idea so save those. As for any other modern postage, use them to send mail. YMMV. Wolf-==-
If the price of the stamps are double catalog only, use them for postage.
If the price is above double catalog, don't use them for postage. They are worth more as collectible stamps.
Some of the recent (last 15-20 years) stamps are sometimes surprisingly scarce as dealer are no longer buying them in bulk. Once their initial supply is sold, replenishing it is difficult, if not impossible, driving up the prices of more recent stamps.
Unfortunately, it is not an across-the-board experience, but a case-by-case basis.