Can i use my account on 2 3DS XL?

Hi, i have the pikachu edition 3ds xl, but i also want to buy the limited zelda edition, but i don't know if i can use my nintendo account on both of them, i NEVER buy games from the eshop, nor plan to, it's just to log in the system using my nintendo account, also, will my friend code change if i register with my account? is the friend code tied to the console itself?
Any other problems you can hink of while owning 2 3ds?
Thanks!