just once is all you need.
You can re-do the attunement like retaking the Energy Awareness Course.
P.S. And no i don’t recommend re-doing the attunement every 15 mins.
How can one possibly “test” where they are “at” or how the field has affected them by doing that?
I think I’ve redone the attunement, maybe 4 or 5 times(?) and i’ve had the card system since it first came out years ago on dreammagick as actual physical cards. So 4-5x in 5-6 years?