Not sure that's fair - the battery packs come with a 5 year warranty. If you increase the 'full range' - you're increasing the odds you'll need to claim on that, which needs paying for.
No it doesn't.
basically the more time that is spent not in the fully discharged state, the longer li-ion will last.
(this doesn't mean you want to leave it 100% charged either, that can also damage the pack; if leaving for extended non-use, leaving it at ~50% state of discharge is the generally recommended advice)
Industrial battery packs extract a fair bit more value from their cells than consumer packs because those customers pay for the extra expense to the manufacturer and they're willing and legally able to accept more complex warranty terms. It's tough to bring something like that to consumers. The fact that this is an option at all shows that competition is increasing along this axis.