How long to charge an iPad air?

Starting from 10% charge level, 2-3 hours is very quick...you are fine with that. If you feel it takes too long, charge overnight instead of during the day. You cannot overcharge so there is not a problem leaving it on the charger overnight. The charging circuit has a builtin in protection that stops the charging when the battery gets to 100%.

Actually, that's very good time for recharging the iPad Air. This having been the second charge means nothing at all in this context. what matters is how low the battery was. Two to three hours is fine.

Indeed. My iPad 4 took over 5 hours on its first full charge.

Note that, like comfy shoes, this will improve as the battery gets "worn in". Until, of course, it gets worn out and gives up the ghost, after which no amount of charging brings it back from the dead.

I don't remember how long it took for the first full charge on my iPad 3, but I know it was much closer to the 5 hours that it took for your iPad to charge than the 2-3 hours it took cessna150 to charge the iPad Air. That is a very quick charge rate.