I have a Maine non-resident Concealed Carry Handgun (CCH) permit that expired last month. I initially applied because it was one of the easiest states to get their non-resident permit, and it was honored in states I needed it for.
I applied around July 2013, and the massive backlog (high demand) pushed the issue date out to 5/2014. Good for four years. It's supposed to take 1-2 months to process, but it took mine almost a year.
Anyway, in October 2015, Maine passed a law to allow permit-less carry for residents and non-residents. Before that, Maine gave gun owners the choice of open carrying without a permit, or concealed carrying with a permit.
So, no need to have that permit renewed.
In my reading, I also found that New Hampshire also has relatively new laws protecting permit-less carry now. I believe in 2017, they started allowing non-residents to conceal carry without permits. That adds a new state to my list of where I can legally carry concealed.
It looks like there are 16 states now that allow at least some form of permit-less concealed carry. Some require the pistol be unloaded (so stupid), some require that you be a resident of that state, and some, like Maine, say as long as you can legally own a gun, you can legally carry it concealed or openly.