Replace air pump switching valves when replacing valve cover gasket?

I recently took the Tundra in for 240,000 mile items. Dealership said this:

"When doing tune up noticed valve cover gaskets leaking internally. When replacing gaskets recommend changing air pump switching valves (known issue for failure) while vehicle is apart to save on labor later."

So my question is, how often do the air pump switching valves fail? What does it cost to replace them on their own? Should I replace them as suggested?

 

Mine failed at around 200k on my 2007 last summer. The Hewitt Bypass kit fixed the issue (must install the block off plates).