When should security systems be replaced?

Howdy again!

I’m not sure if I’ve posted this on this forum before, but my home contains a DSC system that’s about as old as the house itself (about twelve years). It has six zones, one sounder hidden somewhere in the attic, and a dialer that reports to the monitoring company if anything other than Zone 1 is opened while the system is armed.
It is a fairly easy system to use, since the keypads have no confusing LCD, and arming the system is just about as easy is typing in the code.

But my main issue is that it’s old.

I know it would be a huge hassle to replace it, but I think I have another reason for doing so: We have cheap, 120VAC/9VDC ionization smoke alarms scattered throughout the house, and after reading a few articles concerning deadly fires in houses that were “protected” with these devices, I have little confidence that these things would alert us of a fire early enough for us to evacuate.

For instance, a common “aquarium” test was performed by WTHR in which a soldering iron was stuck into a piece of sofa foam in a sealed aquarium containing a CO alarm, an ionization alarm, and a photoelectric alarm and the ionization alarm did not sound at all, even when the CO alarm read 999PPM, the highest it would display. Obviously, a common fire could very easily spell the end for my family.

So my plan involves replacing our DSC system with a newer combination fire/burglary system with i3 and i4 detectors, because they’re heralded as some of the best photo/CO detectors on the market.

I am aware of the cost, but I feel like it’s something that may eventually need to be done.

So my question is this: even if I were to keep our ionization detectors, should a security system ever be replaced?

I don’t think that there is any sort of “expiration date” for security systems, but if you need a more capable panel, it makes sense to upgrade it.
I would recommend going with the Vista 20P with the alpha keypad. Also, make sure a qualified technician does the job for liability purposes.