Hi,
Thanks for your interest in and usage of this community resource.
We know the pattern you describe below is an issue for the network. (Do note that many people do not experience this issue, but enough do so we have been made aware if it.) The crux of the matter is how the captive portal (the router which monitors and controls access to the network) determines if your connection is a new one or not. (If it is new or it thinks you are new, then of course it sends you to the terms of service page.)
Obviously the captive portal gets confused at times. :-/
We have been working on a replacement service which would have you log in (using a Google account), but then would remember your device for an entire week -- you would not have to login in again for that week.
We hope to have this new service rolled out in a couple of weeks. Please keep tuned for an announcement about this.
Thanks again for using this service.