I tried some Googling and searching for this information but found anything (could just be my Google powers suck)

 

I'm currently a subscriber but after I finish the main story and have some okay gear I plan to drop back down to preferred and play more casually until the expansion comes out (this is a secondary MMO for me)

I'm thinking of using my cartel coins to pick up unlocks like the Artifact Equipment Authorisation for myself ready for that time, what I am worried about though is if I buy these and use them when I become preferred again, if I resub after that for the expansion will I lose the upgrades if I go back to to preferred again?

 

It seem unlikely, but I would rather be safe than sorry.

You might ought direct this to Customer Service for a definitive answer but I would fully expect any permanent unlocks you buy to be persistent through however many sub/unsub cycles you go through. I would think that's part of what they're for.

Very good question. I'd like to know this as well.

it's supposed to stick, even if you sub and then unsub... Whether or not it actually works like that is the question...

 

I think there are other threads that have asked this. I dont remember, but some may have been answered by devs.