In 1976 I bought a Gazelle Champion Mondial frame in Holland and hung parts on it from the LBS. I just got back from a 20 miler on it tonight. I even built and trued the wheels. Over the years there are a number of parts that have been replaced but there still are a lot of the late '70s components on it. It still makes me smile.
In more recent times I have found used bikes in fair to moderate condition and set about to tailor them to my liking. This suits my sensibilities more than ground up builds. I figure I will probably scatter the bike to clean and grease it anyway and I can upgrade or replace parts from my parts bin as suits my idea for the bike. So I am doing a ground up build. I just start with a full set of parts that should work together but may need some attention.
My passion is fillet-brazed butted steel frames with non-indexed shifters. I also see no reason to hang more than 7 cogs on a rear wheel.
Whatever you do, think it through well. It may end up being a dear friend for decades!