A stone grind should ONLY be done if the bases are obviously no longer flat, or no longer have structure. Each time a stone grind is done, it takes a layer of material off the bases and the edges, quickly and effectively shortening the life of your skis.
There is no such thing as too much wax on your skis. The bases will absorb the amount they need and the rest should be completely scraped off before use. Waxing is easily done by anyone with an iron, aluminum foil, and a small bar of ski wax. Rub-on and paste waxes are NOT a good substitute....they do not soak into the base itself, they merely coat the surface for about 2-3 runs.
If you only use your skis a couple times a year, take them to a shop to have them evaluated. If they're new, they should need nothing other than a wax job. Older skis may need a stone grind. Otherwise, ask for a hand tune/edge sharpen and wax. For continuing care, wipe your skis thoroughly and carefully after each ski day. Have them waxed at the end of each ski week with the wax left on the bases and the edges. Next time you're ready to go out, scrape them down (a credit card works fine or a ski scraper can be had for around $4) and go ski. This dry/wax cycle should be sufficient to maintain your bases for 1-2 years assuming minimal use and no visible damage. The bases should have a thick coat of wax any time they are stored (oh, and don't store them anywhere damp or stand them on concrete flooring - both will cause rust, even when well waxed).
Fequency of waxing greatly depend on the snow surface that your skis are used on and what they are used for. Race skis get "seasoned" by building up numerous coats of wax and scraping over the course of several months. This fully impregnates the bases and makes the skis slippery and fast. Race skis get waxed before (condition-specific wax) and after (to protect them) every race day. Eastern and Midwest skiers on manmade snow and ice should wax every 1-3 days to prevent "base burn" (the white hairy stuff along the edges). This is caused by friction and actually burns the base near the edge. Western skiers in softer and natural snow can go from several days to several weeks without waxing because the snow is less abrasive. You'll know it's time to wax if your bases are anything other than slick, smooth, and shiny.
