I think if you have enough bikes to choose from to ride, having two of exactly the same ready to ride is a waste of time and money, when you could have one of something else you didn't have already instead.
I'm in a simliar similar situation with one of my bikes because I was building up a certain bike I had always wanted from two basket cases and had gotten about 90% there, when the opportunity to buy a very nice one for good $$$ came up. The 90% bike suddenly became a spares bike with a motor ready to go into the ride bike at short notice.
It is great to keep a spares bike as just that when it comes to things like motor rebuilds because you can be doing the rebuild while you have the other bike still ridable.