I built my second pair of wheels for the week earlier today... I usually set aside 3 hours for this and this includes all the calculations and prep work and the actual build time is usually a few hours if I have all the measurements and parts ready but I like to take a few little breaks as I have trouble standing for longer stretches.

I do this for a living and have taught classes in this as well... I think that most people can learn to build a decent wheel and there are some people who should never touch a spoke wrench.

First time build is probably going to take at least 4 hours but I have had students pick it up immediately and build a sound wheel in less than 2 although they had some help while they were doing that which makes a lot of difference.