I am up to 11 machines now -- yikes. I didn't intend to buy the latest one but I found a lovely Featherweight with case and accessories for $100, so I had to jump on that one.
I have 7 FWs, a Singer 327 and 404, and two Kenmores.
I think as long as you're using them and/or enjoy looking at them, keep them!
But then, I am an enabler.
Ila