This should be quick and easy.
This method requires Paypal
Step 1) Your PP's balance must have at least the amount of the nitro that you wish to get
Step 2) Create another dummy Discord account
Step 3) Using this dummy account and buy the nitro you want as a "GIFT"
Step 4) Copy the gift link and redeem it on the account that you want to have Nitro
Step 5) When Nitro is going to expire, go to your Paypal and chargeback
Step 6) Doing this will remove your nitro away but there will be no ban on the account and possibly ban the Dummy account
Rinse and repeat.
I'm not responsible for whatever happens, use with caution