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In general, leaving any electronics with a lithium ion battery plugged in all the time isn't exactly good for longevity of the battery.
 
Any charging mechanism, used 24/7, will degrade the life of a rechargeable battery. NiCd batteries are the worst in this respect, but they're falling out of favor, tend to be used in low-end devices nowadays, and as far as I know they have never been used in an iPhone.

You'll get better lifetime out of your rechargeable devices if you use them as intended, discharging them entirely now and then. With battery capacity, it's use it or lose it, over time.

In addition, your iPhone will do best if you let it recalibrate the battery once a month or so. To do, just run it down all the way until it shuts itself off. Then charge it undisturbed for a good long while, ideally overnight. Do this a few times and you may find some of your battery go-time is recovered. Same goes for your portable Macs.

One last thing: charging circuits have various degrees of smartness. I have no idea if iHome's charging circuit is as sophisticated as Apple's (or vice versa). They do tend to make good stuff, but it's worth considering.
 
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