A set of handbuilt wheels even with medium quality hubs such as Shimano 105 will last more than two years, easily.
My time doesn't come into the cost calculation either. I don't get paid for spannering and I wouldn't be getting paid for doing something else while I am spannering. I enjoy it, it would be like paying someone to go cycling for me.
My attitude to home wheel building is that I enjoy it, I like the idea of doing it, and I can do it adequately, but it is a process where subtlety and experience play a big part in the skill of doing it, and someone who does it all day every day is always going to be infinitely better at it than I am. Not because they know more about it or because they know some secret I don't, that I want to someday find out, but just simply because they do it all the time. Consequently a wheel that a professional can build in an hour is probably going to be better than a wheel I could build in 3.
It's a bit like fixing your own car - it's something I like the idea of doing myself, but it's just one of those things that someone who does it all the time is always going to be better at.
That said, I probably will do it myself at some point in the future, and I agree that it is fairly therapeutic, it doesn't require a particularly intense degree of concentration, you can do it while listening to the radio or watching telly and just watch it get better and better as you twiddle the spoke key.
