I have lots of backups too...I just fall in love with neat old machines over and over and they have to come home and join the herd And I use them all!
I really enjoy maintaining my old machines too, I can't tell you why exactly, but there's something very satisfying about opening them up and lovingly putting just a dab of grease or a dot of oil in just the right spot and feeling how the motion smooths out. Plus I'm just entranced at the engineering in some of these machines. I think gears and levers are beautiful.
When I go on vacation, it's always a tough decision to decide which machine to bring with me. Usually I bring my most neglected machine and rediscover why I loved it in the first place.
But I have to admit, at home, my 6600 gets the most use of them all and occupies the primo spot in my sewing room. I love my vintage machines, but I love my modern miracle machine too.