What you are asking is quite variable. Each brand and model of rifle barrel is different in composition and coatings.
Weather conditions play a major role.
So, you have to know when YOUR particular sample rifle bore needs cleaning.

Some rifle bores may take longer than others to show corrosion or rust. But damage can be done faster than one thinks.

If you value the rifle, clean it after every firing session or use during a hunt. Multiple shots may require cleaning DURING the session.