Yes, newer units manufactured in the last 10 yrs now have a built in timer that starts counting the minute power is applied which will signal you when that the unit has expired and needs replaced.
I would highly recommend upgrading to one with a DIGITAL READOUT.
The digital readout will let you know down to 1 PPM resolution if it has detected CO well below the alarm thresholds..
here is one that operates from AA batteries with LCD display..
The downside of this one is you have to manually push the backlight button at night, not real handy to remember to look at during nightime.
I have several like this one which is 120V with battery backup that have LED digital readout in my home..
Very nice bright LED readout comes in handy because I do have wood burner, gas furnace as backup heat and gas water heater.. Sometimes if the wood burner stack gets too cool toward the end of the load I lose stack draw.. The CO readouts tells me way before any alarm to take action..
Battery backup allows the detector to continue to operate but display is blanked out and turned on something like once a minute for a second or so.
For LP detection, I would suggest just buying a separate LP gas detector..
