I don't see any mention of 30 days in the Series 60 manual I have. It only talks about changing the oil and filters after "extended storage" and it gives the example "over the winter" without specifying a specific number of days.

In another part of the manual it does recommend removing the batteries if storing it more than 30 days as well as draining the water pump.

I'd love to drive it once a week and get everything up to operating temperature but circumstances don't always allow that. And changing the oil and filters in an inside storage bay is frowned on by the storage facility management.

Too bad there's not another way to keep the top end lubricated. Synthetic oil may help.