I’ve spent over an hour with my housemate experimenting with magnetic poetry two nights in a row. Word of advice, don’t do it (at least, not when you should probably be sleeping)!
I don’t deny that it’s relaxing and fun; but when you have early morning classes the next day, it’s probably not good for you to sleep in the wee hours of that same morning.
I am generally an advocate of writing and expressing yourself through written form. Nevertheless, I recognize the detriment of spending too much time (time that should be invested in other things) on writing for leisure, especially if the words are scattered about on your refrigerator door.