Just locked all my FUN tokens for 360 days. I'm not planning to sell it anytime soon, I keep it mainly because of benefits of Premium Membership. So, why not to use chance to get decent amount of tokens and maybe get even more benefits, like more WOF spins later.
Its a one time promotion so if you want to take advantage of it then simply lock it for 15 days and after it is over then lock it for 360 days
If it's one time promotion, it will expire after 139 hours, or almost 6 days. So, if he will lock tokens for 15 days, later he won't be able to lock it for 360 days because this promotion will expire until it. Unless Freebitco.in will offer it again after some time.