I had heard that cedar shingles needed be restained every couple years. A couple months ago, I looked back and realized it's been four years since we finished building the ADU. Whoops.The stain had started to look tired; the siding needed a makeover. The shingles had lost some of their waterproofing capability and the portions of the structure that experience direct sunlight had started to visually deteriorate. Cedar shingle siding can last as little as 10 years if not maintained, and 40 years or more if it is.