I don't really MM shinies. My first one was a Caterpie that took ten eggs, so I never shut off my DS for that lol
I turn off my 3DS in general since my wiring is kinda messed and it'll turn itself off if I don't, or if I set it down on the right-hand side it'll turn off. I'm not too concerned with it, though. A shiny'll come when it comes :) I've played Korean MMOs so I have more faith in this than in the drop rates of some monsters in that Korean game lol