A backup machine is a must. I must admit I have too many machines, Featherweight, Viking 183, Viking D-1 (my true love machine but it's 20 years old), Viking 875Q (10 inch bed), and Janome 8200 (11 inch bed), Brother Simplicity (weights just 8 lbs. for classes) and a serger.
So I have 2 machines for free motion, 3 machines that I can take to class, and the Viking D1 that still works perfectly but is in retirement right now.
I was doing free motion last week on my Janome and it decided to be finicky and was giving me big trouble. Had to finish the quilt for a wedding so I just pulled out my Viking 875 and finished the quilt. So glad I had it.
I don't go on expensive trips or buy designer clothes so this collection of sewing machines make me happy.