Yes, that’s correct. When someone downloads the app and installs it, the 30 day free trial starts. If there’s no need for the goTenna before your companions head for the woods, they should wait until just before the trip to do so. That way the 30 days runs as long as will be useful during the trip, especially if you’ll be in the boonies for an extended period.
I have 3 phones I use for network testing. There’s one that operates my personal GTM. Another is on top of the Meshmobile semi-permanently. It serves as a relay node wherever it’s parked, plus as a mobile repeater when I’m out of the truck somewhere and using my personal GTM. Finally, I have a donated Android (Samsung G6) that is general;ly left at home because the screen is cracked. It’s what I ping and test message to when I’m analyzing network performance. The first two are on the same account. When I set-up the G6, it steered me towards using my Google address, so that’s why I ended up with two Plus accounts. Still, for testing purposes, this is useful and at $10/year it’s still quite affordable.
There’s something else you’ll also want to download before heading for the sticks, maps for the area you’ll be in. They come in two versions, the standard street map version and topographic. To me, this is the most powerful part of Plus, because the maps on most cellphones go dead once you’re off the grid. Plus I often use topo maps in town, because this helps with evaluating network performance. If you look at other enhanced map service apps, you’ll find that Plus is a relative bargain.