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.
The 45% APY is the one time promotion and not the 360 days locked staking. Even if you decided to lock it on the last minutes before the promotion ended, I think you will still receive the interest for the next full 15 days . Im not sure how this type of promotions works in freebitco.in but this is normally how it works on binance and I think they kinda copy this from Binance.
After the 15 days locked staking ended then you can always switch for the 360 days locked staking