When you make crystal malt at home, you're not going to end up with a grain identical to what you buy in the store. The flavor ends up being a little more toasty and a little less sweet. The color is a bit harder to predict. Also, it's not a time-saving or a money-saving project. Instead, what you gain is flexibility and flavors that you won't be able to find in your local homebrew store. There are few varieties of Belgian crystal malt or crystal Marris Otter, and there is no commercial version of crystal Pilsner malt, as far as I know. So if you want the unique flavors provided by these base malts in crystal form, you'll have to make it yourself.
The process takes about a day, but it requires very little supervision. Newly made crystal malt tends to be a bit astringent, so it will need to age for a few weeks before you use it in a homebrew recipe. Commercial versions are typically aged about six weeks before distribution. For the home made version, plan on waiting two weeks for light crystal and six weeks for darker versions.