They don't. But criminality clearance does expire in 1 year.
If RCMP deems they need fingerprints to successfully issue a criminality clearance, the applicant is sent a fingerprints request. A clearance obtained in such a manner is valid only for 1 year. If a decision is NOT made on the application before this time, RCMP needs a new set of fingerprints to start the criminality clearance process again.
Check the 'Clearances' section in
this link to understand the validity of criminality, security and Immigration clearances.
NOTE : Not everyone receives a fingerprints request.