I agree with all your comments about the economy of rechargeable batteries. There is however a slight problem. A RC battery has a very sharp cut off point i.e. it will work perfectly and then just fail. My application is a motion sensor intruder alarm which can switch on with no problem and can at some point during the night fail. Not a good idea as sods law dictates that will be the night you need it. With a conventional battery it will gradually weaken indicated by a slowly declining beep at switch on over several days giving you plenty of time to renew the batteries which in my alarm last about 5-6 months