Much of the “breakin” is a mental one for new users. People who have had aids typically shorten that. For the new user it can easily take a month. It is getting use to the missing sounds for the new user. All of a sudden, the world is a much louder place. Over the weeks to months, the brain begins to filter sounds as it did when one had good hearing.
Typing on the keyboard and things as simple as shopping cart wheels becomes loud for example. Common remarks is that thing sound tinny for those with a typical loss. Some audiologist will set the gain lower. Newer aids can be set to automatically increase that to full prescription.
For seasoned wearers, it takes a couple of weeks to adjust. Each brand/model has a slightly different approach that one needs to get use too. It is best to get use to the automatic program that all aids have. Well adjusted aids will allow the user to use the one program more than 90% of the time – often 100%. The audiologist is happier forcing that to happen by not adding programs initially.