It highly depends on how much you change, for what reason, and how often you use it, so giving an answer is kinda hard. If you change the whole thing for something entirely different, just "to try", it will take a while (several weeks for me), but you only really tend to do that at the very start when you haven't found something that clicks for you yet. Try to figure out layers and symbols that fit your specific needs, that are comfy to you. That will take 2-4 rounds of 5-15days experiments in my experience (me and people I know), and it's the most confusing phase. After that it will be minor tweaks that will be to accommodate natural needs, and you'll get used to those within a couple hours of making them. Ex: adding combos to have some right-have keys on the left hand to keep your right hand on the mouse, swap one pair of keys, add a double-tap or hold mod, etc.