Hi Everyone, I have a question on cutting boards. I have many HDPE type of plastic cutting boards (used these when I cut meat at IBP the summer between high school and college, so I figured they were good to use as they will not dull knives). I have had them for many years, and some of them have noticable knife marks in them. Some of them I can tell I have run a pizza wheel across them a bunch as they have a spoked wheel impression. What is a good guideline for cutting board lifespan, and when do they need to be discarded? Knife marks, bbq stains from rub / grease, age?