On hard snow at the end of the day, a ski that slips away mid-turn is not a ski that is too difficult: it is an edge that no longer bites. The skier compensates, leans back, tires, and heads home thinking they skied badly. A dry base has the same effect the other way round: the ski drags, you have to push on the flats, and the day feels long.
These are the two most worthwhile kinds of ski servicing, and the two most often neglected.
Your skis go through a Wintersteiger Jupiter. It trims the sidewalls, grinds the base with two successive stones, sharpens the edges with a ceramic disc, then polishes them at exactly the same angle along their whole length.

It can also vary that angle along the ski: sharper underfoot, more forgiving at the tip and tail, for a ski that grips without hooking at the start of the turn.
Waxing is finished by hand: iron, scraping, brushing. This is where real glide is won, and no machine does it better than a technician who knows the day's snow.
For club skiers and racers, we also prepare race skis, with edge angles and base finish agreed with you.