What is PMI?
Usually you don't need to reseat you line cards unless there is an issue and reseating can fix them.
As for cleaning fan, exhaust, etc.... It depends on your environment. If you are building your infrastructure during construction, switches, routers, blades, optics tent to get dirty rather quickly. So, you need to clean them often.
If not, doing it once a year maybe enough. Overall, there is no set rules.
HTH
