Check this thread:
I think it can be relevant.
Most likely you did not follow rclone docs and put your Google client ID in testing which is valid only for one week indeed.
Keeping the application in "Testing" will work as well, but the limitation is that any grants will expire after a week, which can be annoying to refresh constantly. If, for whatever reason, a short grant time is not a problem, then keeping the application in testing mode would also be sufficient.
You decided that it is sufficient for you so live with it:) Please read docs first before complaining.