For years I treated ski servicing as a major chore to be done after a couple of weeks of use, or I would let the shop do it when they were in for repairs after I hit a rock. The problem with this approach is that (a) it takes a lot of work to get the edges sharp again, and (b) the skis don't perform at their best and the edges wear faster.
A better approach is to spend a little time servicing the skis after each day on the hill. The edges can be given a once over with a diamond file (and guide) to restore their sharpness. Leaving it until they are blunt means taking a lot more metal off with the file to get them sharp. Waxing the skis regularly makes the bases faster and does not take too long (but always scrape the wax off when you have finished or they will be slower than if they had not been waxed at all). It is not necessary to wax every day, but it should be done fairly often to get the best out of the skis. Ski racers will often wax their racing skis even if they have not been used, as each wax will make them a little quicker.
Obviously, if you have a ski shop service your skis it is not cost effective to send them in every day, but if you invest in a little equipment, and learn how to use it you can save a lot in shop services. The minimum you need is a file (and guide), an iron (an old clothes iron will do), some wax and a scraper. Ideally you also want a diamond file for finishing off the edges, some brushes for the bases and a vice to hold the skis. Learing how to use all this kit is beyond the scope of this post, but there are plenty of courses and books out there so go Google.
I really need to apply the 'little and often' maxim to this blog as well ;-)