Ah. The 2 year window makes a lot more sense now. That’s about the average time someone who moves frequently might stay somewhere.
And the economics are frequently against making any effort at conservation.
For example, most years I get a communication from the city to please conserve water, especially by restricting watering my lawn. But the amount of water I use is way below the minimum that I am charged for every month (and the city recently raised that minimum quite a bit). They’ve suggested installing timed sprinkler systems. But why should I spend any money to conserve water, or even try conserving it at all? – it doesn’t save me any money to do so. Same with conserving electricity or recycling trash – the city recently cancelled the ‘recycling credit’ they had given for many years on the garbage bill.
There are ecological reasons for doing this conservation, of course, but little economic reason. In effect, such high ‘minimum’ charges are a subsidy of the large energy users at the expense of those who are already limiting their energy consumption.
And that supposed longevity of the CFL may not be real, in some locations. That’s usually calculated assuming an ‘on’ time of some hours, followed by a similar ‘off’ time. But there are many locations where a light has very short on/off cycles. For example, my front entry closet light – that goes on every time someone arrives or leaves the house, but is almost always on for less than 15 seconds. Frequent but very short ‘on’ cycles like that are much harder on a CFL light than an incandescent one. So the much cheaper incandescent light may be better for such locations.
Here’s a really simple way to see the diminishing returns: Right now, you spend $X on energy costs. Conservation measures can decrease X, and save you money… But it’s never going to go negative. No matter what you do, no matter how much you spend, you’re not going to save more than $X total through conservation.