right now is when I get my stand out and go through them, inspect, tighten bolts, check seat. When I buy a new stand or ladder, if there is tubbing exposed, I will use spray foam and fill them up (the caps usually end up missing). If any painting needs done, I do it, so has plenty of time to "rest" and odor to disappear. If I have a stand with a "strap", I replace it every three years (I don't leave stand out longer than a week), I change them as a cheap insurance policy, then use the old ones for other things. I will go through and inspect my harness at this time as well. I work in a manufacturing plant and we do this every year at work, I strongly recommend you do this once a year as well. If anything look's out of place, discolored straps, or threading loose, I throw it away and buy another one.