Hi Paul I am also busy building a 5' B1. When i started off I was talking to one of the old timer at our local steam club. I thought he was crazy when he said the loco would only take on avarage 5years to make, of which the first 10 years is the hardest. I did not understand what he meant. But after 2 years I understand. It is a big project, but off all the loco's I have looked at it seems to be a great loco to build. The biggest problems is that we are never happy with our workshop or the tooling in it. You will always need some special tool and machine and like most of us we will want to make a better version or cannot afford to buy it.
Understand taht the cost of a workshop is very expensive, and the model part like the castings prices have gone crazy. Not many people can afford the luxury of building any type of model, even Lego costs a arm and a leg.
But ll said my greatest pleasure is the time spend in my workshop and It does not matter how long it takes or how many :"_)*%$#@@ I make the pleasue and satisfaction of making even the smallest part is worth it.
Last of all don't show your wife any thing you have made as the look on her face will not impress you. Taking the completed part to your local club there again will get difficrent reaction. Half the people will be impressed and supportive and half will criticise.
Good luck and enjoy the journey