Set up an AYIYA tunnel, it won't get deleted due to inactivity, but it'll be with one PoP only. There *is* MobileIPv6, but it's not really ready with Linux yet, and I don't know how far along MacOS is.

Why do you think that a tunnel that is up only a little bit gets 'deleted'? Static tunnels indeed have a requirement that they are pingable (this because when the tunnel replies to ICMPv6, most very likely the host at that IPv4 address is the one you are running and not somebody else, which would cause abuse reports to be sent to us for sending 'hacking packets!' and other weird abuse complaints we got in the past). Dynamic tunnels (AYIYA, heartbeat) though are free from that restriction and also don't earn that many credits. AYIYA tunnels especially can be perfectly used for 'mobility', this at least works fairly good in the same country, if going abroad you still tend to generally connect to the resources you connect to normally, which generally are also in that country, thus latency overhead will not be too bad. Truly dynamic tunnels (thus the ones that automatically set up and disappear again) are impossible at the moment due to abuse handling. Next to that all requests are manually approved so that we are able to select the best PoP for the endpoint, next to PoPs having their rules which endpoints/users they serve.

For roaming access to IPv6, try teredo. Once I installed miredo (the Linux teredo daemon) on my laptop, I got IPv6 access everywhere. No static IPv6 address, but that's fine since there is absolutely zero configuration necessary. I don't know about teredo for mac, but it might be worth researching.