The "kit", as you call it, is normally setup to achieve something close to a THR crossing height of about 50 feet. The actual location of the GP will be a function of the ground elevation in the vicinity of the GP site and the THR elevation. The LLZ (or LOC, if you prefer) is setup to provide a standard path width at the THR, so the LLZ/LOC position will be a function of the length of the runway itself.
ICAO requires calibration checks every 6 months. This entails a full check every 12 months and a slightly abbreviated check in between times.
If the setup has been done right in the first place and the alarm monitors haven't been monkeyed with in between times, very little "tweaking" is usually necessary. Sadly, this isn't always the case so, yes, it can be a case of having the calibration aircraft fly many approaches and direct the technicians to make appropriate adjustments to course width and/or approach path.
There's a bit more to it than that, but that's the general guts of it.