Gmail Doesn't Receive Emails Frequently Enough from My External POP3 Email Account

This article from Lifehacker (Make Gmail Check Your POP Accounts More Frequently)
helped me solve an ongoing problem where Gmail was only checking a branded, external email address (POP3 mailbox) about once an hour.  Clients and prospective clients were sending me emails to collaborate on projects and I wasn't receiving anything right away.  Emails were taking 10-60 minutes to be retrieved.

It was frustrating to have to go to Settings > Accounts and Import and manually tell Gmail to fetch more mails from my email address at another domain.

There's also this option in the Labs options section. [source]