Hello Mate. All that's needed is something to reassure the user that the kit gets looked at regularly. The sticker should say something suitably soothing but succinct, like
TESTED. Way back in the army, we found that
SERVICEABLE really conveyed all that needed to be said. That plus the tech's initials, of course.
But whichever sticker you apply, always simply put the "tested on" date on there. That is, don't add the "next date due". Unless, of course, you want it to come back and bite you in the butt later on (
ie, when the date has come and gone)!
