When to refresh an access token?

Hi all,

According to the docs, An access token, if not used, will expire in 24 hours.  In addition, according to information from CC staff here in the forum, an access token will expire two hours after it has been used.

So how often should my application refresh the access token?

It doesn't seem reliable (or performant) to refresh an access token before each API call so I'm assuming most folks setup a refresh token script which runs automatically on a set schedule (such as a cron job).  Am I right in this?  If that's the case, how often do you run the script, every hour?

Please advise.