Formal:
* Frequently: This is a more formal synonym for "often."
* Regularly: This emphasizes a recurring pattern.
* Periodically: This indicates that something happens at intervals.
Informal:
* A lot: This is a casual way to say "often."
* Many times: This emphasizes the number of occurrences.
* Repeatedly: This emphasizes the act of doing something again and again.
* Always: This is a stronger word than "often" and means something happens every time.
Other:
* Customarily: This implies a habitual or established practice.
* Habitually: This suggests a regular, ingrained behavior.
* Typically: This implies that something is characteristically done.
The best word to use will depend on the specific situation and the tone you want to achieve.