You could buy alarms with replaceable batteries, change the batteries once a year, and the alarms all at whatever multi-year interval makes sense at the first of the year. Put the change dates on your calendar and on the device. I use Nest Protects at home for the ease of use, but I'm guessing there are cheaper options with wireless networking.yeah I'm planning on putting redundant alarms in the slide out cabinet area where the furnace, electrical, and LP lines are all spiderwebbed.. if I get a fire it'll start in there..
I'll be mounting a piece of ply on the surface where the Smart Solar and BP are in my previous pics.. run it all the way to the floor.. then both sides of it I can use for a wiring base.. gonna put em down there.
One thing I'm trying to avoid tho is buying a bunch of alarms at same time, cuz then the'll all expire at same time.. if going for redundancy I'd like to stagger the expiration dates, so start of next season will be a great time to put em in.
My house is split level and I upgraded to networked alarms since I'm sleeping like 4 floors from basement, unfortunately I bought em all at same time and all the co2 alarms expired right after eachother and they are not cheap..