Proper method of exercising thru-hull valves?

[Beautiful Day]

What is the recommended interval of exercising thru-hull valves? Once a month? Once a quarter? Twice a year? Also...I can detect a distinct difference in the extra resistance the first time I move the handle. But, is there a minimum or recommended number of times the valve handle should thereafter be opened/closed in the process of "exercising" these valves?

 

[Ralph Johnstone]

But, is there a minimum or recommended number of times the valve handle should thereafter be opened/closed in the process of "exercising" these valves?

For the sake of your boat, they should be exercised every time you leave the boat.

Remember that most sinkings occur while the boat is tied to the dock .

 

[Joe]

I close mine every time I button up the boat before heading home.

 

[Maine Sail]

I close mine every time I button up the boat before heading home.

Ditto and this is more than enough exercise... Kill two birds with one stone...