How long do firebase credentials remain on web client

How long do the firebase credentials last in the web client, I am making a web application that is planning to stay offline for months and when they get back online it will be updated. What I need to know is how long they last, can the time be increased?.

I have looked in the firebase documentation but I have not been able to find the desired information

I mean these credentials https://i.stack.imgur.com/dZqH5.png