Review the needs of your site before you decide how often to issue sp_text_notify.
Using sp_text_notify produces a load on the Enhanced Full-Text Search engine as the system procedure reads the data and updates the text collections. Depending on the size of this load, the performance hit for issuing sp_text_notify can be substantial. Because of the performance implications, you must determine how up-to-date the indexes need to be. If they must be close to real-time, then issue sp_text_notify frequently (as often as every 5 seconds). However, if your indexes do not need to be that current, you may want to wait until the system is not active before you issue sp_text_notify.
You cannot issue sp_text_notify from within a transaction.