It's possible to transfer your Plus purchase to another account. This is useful when your old account got hacked and you created a new account. This is also possible if you've won Plus through a giveaway.
How to request a transfer
Open a support request via the following link and fill in the required information.
In order to validate you own both accounts, you need to follow this Spotify profile with both accounts. After the transfer is done, you can unfollow it if you'd like :)
Can you transfer my stats too?
Unfortunately, it's not possible to transfer your stats right now. If you want to merge your stats from your old account into your new one, your only option is to request your endsong files from your old account and upload them into your new account.