You're not supposed to have to clean it regularly.
The important thing is to make sure that the screw is really tight. i mean REALLY TIGHT
Yes, that screw has to make very good contact and press that contact-areas really good at each other to prevent air from getting to that areas.
But i would love to hear/read a detailed torque-value from the manufacturer for that screw...
Because REALLY TIGHT might be somewhere between 5Nm and 15Nm for various persons.
Whats that screws size again? M5? Just to mention:
The maximum nominal torque for a M5 stainless-screw is 4,9Nm for a strength-class 70 and 6,5Nm for class 80.
And even this low torques only apply to short screws, length <= 8 x diameter. Longer screw, lower nominal torque.
The top-threads are in an aluminum-part. And short thread lengths in aluminum are not very torque-resistive, too.
e.g.
If i tighten a screw as hard as i can just with one hand and a screwdriver, i reach 12Nm. That's a good way to rip that screws head off.
Sure, most people won't tighten that screw that hard, but some might
So, as i said, i would be REALLY happy to read an exact value for that screws torque.