Threw in a fresh discount store AAA battery to see how long the Advisor will run. The "POGSAC keepalive" was set to 14 minutes, but turned out that after ~22 hours the pager began to vibrate (weaker than usually) every few seconds. The battery voltage had dropped low enough that when Arduino had sent the null message, it tried to reboot, but Arduino+LoRa module drew too much current, causing pager to reset constantly. Multimeter showed 0.6-0.7 volts in the battery.

Not sure if the keepalive thing is required due to this obvious sign... I dunno, use it or don't.

Anyway, 22 hours is good enough for gags, a night out, etc. I bet the most power hungy part is the LoRa module. It does have a sleep mode, but I don't think it'll receive while sleeping. Would it wake up on looooong preamble or something? No idea. Might look into that later when I have time.