For you, but my kids don't use their 3ds's like that. I don't fill them with ever possible game. I do it in packs, it keeps them more interested.. and with as much time as it takes to fill that huge mSD your even in worse shape if and when your sd card dies, you will be doing it all again at an extreme amount of time, for me with GW, I will be too, but 30-35 times quicker than you.
Example:
128 Gig mSD card: time to fill on freeshop at 3 megabytes per second - would take 711 minutes or 12 hours. I am guessing in reality for most it would be much longer, I am being nice by saying a constant 3 Megabytes per second. Still 12 hours.. Probably really like 18.
128 Gig mSD card to copy over from my computer at 45 Megabytes per second - takes 47 minutes