They can be used to mail First Class letters no matter what the postal rate.
A forever stamp is a stamp that is valued (sold and cancelled)  at the current local letter rate of postage. For example, if the  current cost of local postage is 50 cent … s, the forever stamp is  valued at 50 cents. Effectively, yes. Strictly speaking, a forever stamp is only one that bears the word Forever, but like the forever stamp, the Breast Cancer Research stamp is good for 1 oz f … irst class US postage at any time, regardless of the price when you bought it. The current price for a forever stamp is .44 cents (2010) so 20 years from now the value of that same stamp will still be .44 cents, even if the price for one ounce is $2 then. So, you would need five forever stamps from this year for 1 ounce in 20 years. Post 55. @Post 37: That flag USA first-class stamp is not a forever stamp. I have those and they are worth 41 cents. Only stamps that actually say Forever are forever stamps and their value = the current value of a 1 oz letter stamp (right now it's 44 cents). First Class is currently worth 42c. Forever Stamp is worth First Class, even if it's value increases. Older First Class Stamps are worth what they were worth. (The current First Class Stamp has a flag and clouds) The USPS is usually lenient on a few cents, so the older First Class stamps are usually counted as being worth 42c. The current rate of postage, mailing from US to another US adress, is 42c. (First Class Rate). Forever Stamps were created by the United States Postal Service ® (USPS ®) in 2007. They are non-denominational First Class ® postage, which means that they can be used to mail First Class letters no matter what the postal rate. For example, in 2013 it cost $0.46 to mail a normal-sized letter weighing one ounce or less to an address within the United States. In 2014, the rate increased to $0.49. Avoid placing two Forever Stamps on a mail piece for heavier mail. Additional ounces are much cheaper costing only $0.22 per additional ounce rather than $0.49 for one ounce letter. If you add two Forever Stamps to a 2 ounce letter, you would be paying $0.98 for an item that should only cost $0.71 As for the Forever stamps (the ones that actually say forever on them), they will always be worth the postage rate of the current 1 oz. First Class single-piece letter. You can use one for a letter that is 1.0 oz. or less. Post 55. @Post 37: That flag USA first-class stamp is not a forever stamp. I have those and they are worth 41 cents. Only stamps that actually say Forever are forever stamps and their value = the current value of a 1 oz letter stamp (right now it's 44 cents). @anon106653: A forever stamp holds it's value forever; that is why it is called a forever stamp. If it only held the value of the year it was made it would be a first class stamp. You do not add any other stamps to it when mailing a letter 1 ounce or below. Post 55. @Post 37: That flag USA first-class stamp is not a forever stamp. I have those and they are worth 41 cents. Only stamps that actually say Forever are forever stamps and their value = the current value of a 1 oz letter stamp (right now it's 44 cents). The  forever stamp is forever valued at that rate.  So, before the price goes up, buy a lot of forever stamps and  you will save money. Forever stamps also save having to use 1 or 2  cent stamps to cover the postage increase. Saves you and the post  office time and money. Effectively, yes. Strictly speaking, a forever stamp is only one that bears the word Forever, but like the forever stamp, the Breast Cancer Research stamp is good for 1 oz f … irst class US postage at any time, regardless of the price when you bought it. Forever Stamps are ideal for mailing normal-sized, one-ounce letters within the United States. If you suspect that your letter may weigh more than one ounce, be sure to weigh it prior to affixing a Forever Stamp, as heavier letters will be returned due to lack of postage. Avoid placing two Forever Stamps on a mail piece for heavier mail. Additional ounces are much cheaper costing only $0.22 per additional ounce rather than $0.49 for one ounce letter. If you add two Forever Stamps to a 2 ounce letter, you would be paying $0.98 for an item that should only cost $0.71
http://www.answers.com/Q/How_do_you_know_if_you_have_a_forever_stamp http://www.wisegeek.org/what-is-a-forever-stamp.htm https://answers.yahoo.com/question/index?qid=20090127200244AAVOKyR http://www.stamps.com/usps/forever-stamps/ http://www.wisegeek.org/what-is-a-forever-stamp.htm http://www.wisegeek.org/what-is-a-forever-stamp.htm http://www.answers.com/Q/How_do_you_know_if_you_have_a_forever_stamp http://www.stamps.com/usps/forever-stamps/
how do you know if a stamp is a forever stamp