Sooner than in milder climates. Freeze-thaw cycles pry at the surface all winter, and the UV at this altitude breaks sealers down faster than the product labels assume. 

Industry guidance for stamped concrete generally lands around every two to three years, but sun exposure, shade, and traffic all move that number. 

When we look at your patio, we'll tell you honestly where it is in its cycle, including when the answer is "you don't need us yet."