"I rarely turn the feature off. If the game is in 3D (AC or any other game I play), I'll play it in 3D. I love AC in 3D--it's one of the best things about the game."
that's exactly the same with me. i don't think i've ever turned the 3D off. i bought a 3DS to play 3D games. not 2D. so i love having it on, it enhances the depth and detail of the game, in my opinion. if it drains the battery, i don't care. my battery is always drained because i play it so much. so more than half the time i play it, it's sitting on a charger anyway. the 3D has never strained my eyes, and still doesn't. i don't hop around or move about or anything when i play, i relax either on a comfy chair or on my bed, so it's easy to hold the 3DS at a respectable distance. i've also noticed that if you don't have 3D on and you take pictures, the pictures end up looking grainy. but that's just me.