I "almost" upgraded to that phone, but found a refurb T399 Galaxy Light for $55 shipped. First smart phone in the family, we all have a pc, notebook, and tablets, so use our phones to talk or text, not surf etc. So far having a lot of fun with the phone but no actual use, just wrong numbers.
I've got spare batteries for things like cameras, but I can't see owning a spare phone battery vs access to charging devices. Now that basically everything can be charged from a USB vs the old days of proprietary chargers, not an issue.
OTOH as soon as essential devices start to show lower battery capacity I replace the batteries with new usually better ones.