39 CFR 551.5 - Frequency and other limitations.
(a) The Postal Service is authorized to issue semipostal stamps for a 10-year period beginning on the date on which semipostal stamps are first sold to the public under 39 U.S.C. 416. The 10-year period will commence after the sales period of the Breast Cancer Research stamp is concluded in accordance with the Stamp Out Breast Cancer Act, and as amended by the Semipostal Authorization Act, the Breast Cancer Research Stamp Act of 2001, and Public Law 107-67, section 650, 115 Stat. 514. The Office of Stamp Services will determine the date of commencement of the 10-year period.
(b) The Postal Service will offer only one semipostal stamp for sale at any given time during the 10-year period.
(c) The sales period for any given semipostal stamp is limited to no more than 2 years, as determined by the office of Stamp Services.
(d) Prior to or after the issuance of a given semipostal stamp, the Postal Service reserves the right to withdraw the semipostal stamp from sale, or to reduce the sales period, if, inter alia:
(1) Its sales or revenue statistics are lower than expected,
(2) The sales or revenue projections are lower than previously expected, or
(3) The cause or recipient executive agency does not further, or comply with, the statutory purposes or requirements of the Semipostal Authorization Act. The decision to withdraw a semipostal stamp is to be made by the postmaster general, after review of supporting documentation prepared by the office of Stamp Services.