x310 mower problem

The PTO on my x310 is sometimes not engaging and I have to engage the control button several times. What to do?

Replace the switch.
They are crude rude & unsofisticated simple slide switches which carry heavy current so eventually burn out.
IT is held in by a couple of barbs on the short sides of the switch so you squeeze then in & push it up then disconnect the wires.
Not as easy as it sounds.
All PTO switches are wired the same so you just need to get one with the same pin layout.
Handle colour makes no difference to the switch.

Is it likely the switch would go bad so soon, only 40
hours on the machine?

OK if you really want help we need to know everything cause we are here and all we know is what you tell us.
And yes it is possible that the switch is burned out.
It is also possible that the switch has an ants nest in there ( yes it happened to some on on this forum )
IT is possible that the switch corroded from being damp and not being used.

You posted a problem & I posted a solution.
Having a spare will not cause the plane to stop rotating is the switch is found to be OK.

Other than that JD make excellent technical manuals that give you step by step instructions for testing & repairing your mower.
It is around $ 40 as a CD or download & $ 100 as a printed book .
However it will pay for itself the first time you use it and 10 times over if it allows you to keep your mower running for a long time.