USCG accepts 2-year First Aid/CPR courses for 1 year only. It's a rule under 46 CFR 11.201.
All approved courses for domestic USCG licenses are only valid to be submitted to the USCG for one (1) year after the issued date.

This comes from 46 CFR § 11.201 - General requirements for national and STCW officer endorsements.
We completely agree that it is frustrating as CPR and First Aid training courses are good for 2 years but only accepted by the USCG for your original captains license for 1 year after issuance.
The best place to look for course expiration is the course approval information on your course certificate which most schools write out on their certificates. It's a paragraph and the it will typically say "must be submitted within one (1) year of the date shown" or "must be submitted within five (5) years of the date shown".
Any course certificate or training related to a 6 pack, 100 ton Master or 200 ton Master will always need to be submitted within one (1) year.
If your training is for any license above these or for the International STCW endorsements there is a possibility that it could be valid for 5 years.

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Nate Gilman is President and Co-Founder of MM-SEAS. He hawsepiped from the deck to a 3rd Mate Unlimited license with full STCW compliance over more than 15 years at sea, and is a veteran of the NOAA Commissioned Corps. He works directly with the National Maritime Center, USCG-approved training schools, and vessel operators on credentialing policy, and writes on sea service documentation, evaluation standards, and how mariners move up the license ladder.