As well-intentioned as the new law may be, it could just as easily cost as many lives as it could save. The price of the 10-year detectors will probably discourage people from replacing them at their end of life. because the 10-years devices are not cheap. Sure, you can talk about the cost of replacement batteries for the old units, but that will be an incremental cost spread over ten years. People with lower incomes will have sticker shock when they try to buy a 10-year replacement. MORE HOMES WILL END UP WITH NO DETECTORS.
As a Fire Prevention Officer and Fire Inspector having a 10 year maintenance free smoke detector could saves lives. I have seen in the past when investigating fires where smoke detectors were installed but did not have batteries. This is a common issue when the detector starts beeping and occupants either do not have a replacement battery or simply removes it and forgets to replace it later. The other concern is for seniors or those that need assistance that might get injured when they fall off a ladder or chair while trying to replace the batteries twice a year as recommended. The cost is more for a 10 year detector but in the long run for the cost of 2 batteries a year for 10 years it is worth it.