There are two different types of Exchange backup.  Database Backup and Log Backup. 

Generally, it is best to backup the database as often as possible, as this type of backup is the easiest to restore.  But it may only be practical to back this up once a day, or even once a week. 

Log backups take a very short about of time and require very little system resources.  Why not add an 'every 1 hour' backup rule to a log backup set for your exchange.  This gives you multiple restore points throughout the day.  In the event where something does go wrong, you may have lost only a few minutes of exchange data rather than a whole day.