Warning! Reality Mismatch!
And the problem is exacerbated because alarms are designed to be installed and last 10 to 15 years. That means a lot of legacy products, compared to the two to three year product lifetime we are seeing on general IoT products.
I suggest this shows just how far from the real world many IoT pundits and 'toy' developers are. The sorts of things IoT is being targeted at are things that currently are, quite reasonably, expected to work with minimal maintenance for a minimum of 10 to 15 years in a domestic environment and significantly longer (30+ years) in many industries.
By way of example, whilst the circuit board in the external box need to be replaced every ten years or so (degradation due to sun and weather) the alarm control box, under the stairs, I don't expect to do anything to it until some component (eg. it's PSU) fails, which shouldn't be within a few decades.
Similarly light bulbs might have a 'limited' lit life, but that doesn't mean that they don't last; I still have a couple of bulbs I've not changed since I moving into my current house 12 years ago, because they just don't get used very much. My central heating controls are still the originals and I see no need to replace them anytime soon.
Which gives rise to an interesting security problem, namely: within the life of these systems we can expect commodity computational power to develop to the point where the "state-of-the-art" security installed in them can be broken by any one simply downloading the relevant cracking tool.