The longest I have kept a wood board is 4 years. Three formula boards - 175, 147 and 160. I moved up just to get a newer, better board. I still love my 160 and have no interest in a new one since I only race a few times a year and the 160 is still a great board and in excellent condition.
My iS 111 is almost three years old and still looks as good as new. I Don't know when I will get a new one, but certainly not in the next year.
Last year, I sail my formula board 22 days and my iS 111 30 days. I record all my stats including GPS info. My other boards, another 27 days.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.