Instagram has updated their inactive username policy to indirectly state that it no longer removes accounts after prolonged inactivity. The company’s new policy only states that it encourages people to log in and use Instagram once they create an account, while previously it stated that “Accounts may be permanently removed due to prolonged inactivity.”
The previous username policy ensured that if a person is not using his Instagram account enough, the username will be freed up for anyone to take. But that’s not going to happen anymore with the new policy in effect.
So if you have got a username in mind for your future business/startup, you can register it now on Instagram. It won’t be removed even if you don’t use it for the next few years.