my brother told me (for our school ski team, not in general) that i should ski the same every time we went, except for actaul races. then you switch them up so your riding on fresher edges (since they don't wear down as fast and i wasnt going to sharpen every time i went out).
as for park, ehhh, who cares. i mean a lot of skis have graphics on them that are meant to go a certain way so if you switch it up, thats gonna look weird. and your edges should be fairly dull for park anyway
the only thing i have found is that my skis chip on the inside edges of my skis, so if i switched it up it would chip more evenly.