If you don't have any splitting, then leave well enough alone. If you have mildew and UV 'damage', it's time to clean the siding and re-seal/stain. The pros are it will prevent the siding from having a 'short life' and it will look nice. The cons are the opposite, I guess. Maybe I'm not fully understanding what you're asking.
If you want to say more, please do. My best to ya and hope this helps.