What is the best method for keeping a purchased 2FA account active?

Here's some basics, get aged accounts whenever you can. Warm up the accounts*, make sure your verification method is solid if you hire verification services, configure your anti-detect browsers correctly and make sure you're using good IPs or just use a mobile proxy. Do whichever ones apply to you and you're good for starters. Best of luck.

In order for your business to operate more effectively, you should find reputable agents, where you will receive useful advice and good service.

After having an account, you need to use it for a while to log in on the device to avoid FB seeing abnormalities.