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You might get as many answers as there are skiers. From my point of view, you can look at how often to wax two ways:
1. Never. This actually works for wax.(not so true for edges) Your bases get conditioned to a certain point and then just sort of stay there. Trust me, I went about 10 years without waxing. Your skis won't be great sliders, but they are OK, and more importantly they are never "sticky". Some will say the base gets oxidized, or some tech term that means bad, but I haven't experienced it and I believe it is more hear say than fact. The skis won't be great sliders, but they rarely will be poor sliders. If you are not demanding a lot of performance from your skis (ie. you are in the learning phase) then the benefits may not be worth the effort.
2. Roughly every 3-5 days of skiing. Waxing at the beginning of a week long trip is a good idea and the skis should be fine for the rest of the week. Once you commit to waxing, then your ski life becomes more complicated. There are certainly benefits to be had in the performance of the skis, but there are lots of variables to waxing and you are committing to getting up to speed on them. Not to scare you, but the wrong wax can make a ski day a disaster (speaking from personal experience with super sticky skis). Once I committed to waxing, (and doing it myself) I felt overwhelmed for a while with all the different waxes on the market and when to use which wax. My biggest hurtle was getting my glide wax to last for just ONE full day of skiing. I will pass this tip along so you don't get bogged down by it. Turns out wax likes to stick to wax, but it doesn't really like to stick to ski base plastic (hence why you can get away with never waxing). So to get it to stick to your ski bases, you have to use soft "runny" wax that penetrates deeply into the ski base. This is called "base prep" wax (I think this is what "Swix MB77" mentioned before is) and is called prepping your bases. You typically only have to do this once a season. Once this is done, you put on your "glide" wax and it sticks really well to the penetrated base prep wax. Once I did the base prep wax, my improved glide went from barely lasting a day to lasting 3-4 days. It took me 2-3 seasons and a few posts on the defunct Epic site to get educated about this. If you heard the term "hot boxing", this is a ski racers way of doing a base prep and maybe glide wax treatment?
I now am fully committed to waxing my skis every few days, I know how to choose which wax for the conditions, and I glide on run outs faster than most people. I really do like the way my skis feel on the snow now, and can easily tell when I need to apply more wax (or I haven't put on the correct wax). I don't know if I am happier now, or for the 10 years of not waxing, but my skis are for sure a lot more slippery. I will say I enjoy spring skiing a lot more now, as the snow can get really sticky and the right wax can really make that almost go away.