Replacing CO detector - IQ2+ system

I have several CO detectors connecting to a Qolsys IQ2+ panel (with 319.5). Across three homes, it’s about 10 units - all DSC PG9933.

Installed about four years ago, they are apparently reaching end of life. In one home, all four died within minutes of each other. In another location, two of the three failed at the same time. I’m sure it’s a matter of days before the rest die.

I’m torn about replacements. Current cost is about double what I paid four years ago. I like the idea of the units being tied into the system, but am seriously looking at the $20 plug-in units I can buy at Home Depot.

Is a replacement DSC unit really worth the $1,300 vs $100 total cost?

Another option is the QS5210-840 which is on the Surety website for $77 each. Much more than the $20 units, but still better than the DSC.

What are the pros/cons of DSC vs IQ vs non-connected option?

If you need the extra range, the PowerG model is recommended, but for most purposes either the PowerG or IQ CO detector will be good.

Cheaper incompatible models will also have an expiration date, and would not be monitored by the panel. Some people will install one or two monitored detectors in common areas of concern like the basement and outside bedrooms, and then cheaper models elsewhere.

PowerG has better range, less interference concern, potentially better battery life, which is usually a great bonus for other types of sensors, but on a detector with a 5 year expiration date the battery life is not usually impactful.

Thank you!