In addition to what has been said, you may also want to check that your phone has
good 3G/4G reception. I have found this to be the most common cause of heating (both for the HTC 8s and the L1020), i.e. when signals drop (or worse, disappear completely), the phone begins searching for better cellular sites (or other permitted networks) to connect to - this
activates the power-intensive 3G/4G antenna longer than usual, which then puts a
heavy load on the battery causing it to heat up quickly.
As for the scratching, I am not aware of the type of glass used as the lens cover for the L730. For the L1020, I suspect its also Gorilla Glass (or some hardened glass variant) since it seems to have all the properties of a Gorilla glass screen: anti-reflective, oleophobic and scratch resistant. So, being a newer phone, the L730
might be have Gorilla glass, too, as the lens cover. If this is the case, it would take a HUGE amount of effort to scratch it... unless what you're seeing aren't real scratches but merely smudged pieces of sticky dirt (such as dried rice or other similarly dried pasty material). Nevertheless,
a scratch doesn't appear on its own, as said by Fred Wilson2, so I'd be mindful of where I place my phone.
Small bits of dust, especially sand, on a flat surface (e.g. a table) where you place your phone on is enough to scratch even Gorilla glass, since sand and some dust particles contain quartz - softer than Gorilla glass but small and hard enough to scratch it.
As for me, I have never placed my phone on a flat surface without my leather pouch for it to rest on... or even better I keep my phone inside the leather pouch as much as I can. Result: zero scratches both in front and the back, almost seven months and counting.
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