How long should new valve cover gaskets last?

How long should new valve cover gaskets last? Had new gaskets installed on 11/09/21. Only 10,988 miles since replacement. Went in for oil change & now they informed me they are leaking...again.
Of corse the warranty is for 12 months /12,000 miles. So I'm under the 12k miles but 12 months past time frame.
08 Tundra so the 1st set of valve cover gaskets lasted 13 years & 142,000 miles.
Waiting to hear back from service manager.
Any thoughts ....?

 

Did they FIP the half moons and front corners? Also what about spark plug tubes?

 

Not sure...
My invoice from 11/21 states there was oil leaking from the valve cover gaskets both sides. Note states valve cover gaskets & half moons (All)
Removed & replaced both Bank valve cover gaskets with all tube seals and gaskets required with new gaskets & replaced all spark plugs.
Note shows charges for spark plugs, spark plug gaskets, FIPG oil pan & valve cover gaskets.

 

Clean it with engine cleaner and then watch to see if it reaccumulates.

 

4.7 or 5.7? 4.7 if they forgot the half moons will leak.


5.7.. potentially not a valve cover leak but a cam tower leak misdiagnosed the first time

 

Theoretically it should last just as long as original if done correctly....

 

My bad didn’t notice he’s not FGT.

 

I have the 4.7
Thanks for all the feedback. At least now when I go back I can ask more specific questions on where the leaks actually are. Based of your feedback, I would think that if the leaks are ;
* around the half moons or the front corners the FIPG may not have been done properly.
* around the spark plug tubes, tube gaskets may not have been seated properly.
* around valve cover gaskets, not seated properly, valve cover bolt washers not replaced or torqued properly...

Your thoughts or feedback appreciated.

 

Got a better look this morning.
Passenger side leaking in front corner and also about mid way down valve cover gasket.
Driver side leaking about midway down valve cover gasket.
Didn't see any leaks around half moons or spark plug gaskets.
Valve cover bolts seem tight.
Any thoughts on what would cause valve cover gaskets to leak so soon ?

 

Using non-OEM gaskets. Perhaps overtightening - bolts have integrated rubber water that gets hard. Replace those too.