Is there a limit to how frequently I can backup?

No, but if you backup more frequently (e.g., hourly instead of daily), we strongly recommend creating full backups more frequently - daily or weekly instead of monthly (I.e., the default).

The reason is that long backup chains are inefficient and more vulnerable if something goes wrong as links in the chain depend on one another.

If you backup daily, and do a full backup monthly, your backup chains will consist of a full backup with at most 31 incremental backups linked to it. But if you backup hourly, by the end of the month your backup chain could consist of up to 744 incremental backups, all of which have to be downloaded and extracted when you restore.

To configure automatic hourly backups with a full backup every 7 days:

mv /etc/cron.daily/tklbam-backup /etc/cron.hourly
chmod +x /etc/cron.hourly/tklbam-backup

echo full-backup 7D >> /etc/tklbam/conf