Most of the wilderness FA certs have a 3-year expiration. IDK if this was always true, but it's definitely a thing now.

If you're using your certification to qualify for a professional or volunteer position, then they usually defer to the expiry period set by the issuer of the certification.

In my experience, basically nobody gets any first aid practice, in between re-certifications. And these are perishable skills, so I wouldn't trust in the ability of most people to execute anything complex after even a year has gone by... But that has to be balanced against the cost of re-training. WMR is usually an 80-hour course (IIRC) and re-certs more like 30-40? That's an absurd time investment for most working people.