Keeping backup equipment?

I like to have a backup for certain components on hand.  I don't like to be without music at home, so if my integrated amp or my phono stage were to give out, I would need to start shopping (not a bad thing, of course).  But I keep a (B-stock) Yamaha A-S701 and a Schiit Mani on hand as backups.  They also serve as a good basis for comparison to whatever gear I have in my main setup.  

In addition, I try to keep my stereo spending as close to budget neutral as possible, so I sometimes sell something before deciding what to purchase to replace it.  With the backup gear, I can keep the music playing and take my time to make a good decision and find a good deal on the next component.

I keep some older components as backups. I hold on to any component that won't make much money when resold
Right now I have four amps that I upgraded stacked in my back room.

Doesn't hurt to keep something around just in case. Doing some spring cleaning, I came across an older Teac CD player (half width model) that I thought had a channel go out and when I tried it out, the sound was very impressive and almost to the level of my Marantz SA15S2b SACD player. 
Nice to know if the Marantz goes sideways.

All the best,
Nonoise

I eould keep spares for investigative AND backup purposes. You have to do what you feel comfortable with. Sell the Vidar and replace it with a cheaper one to reclaim a small sum.
But...  
If your main amp failed could you live with it?

Gday, from Australia. 
I have a Parasound P6 as a spare, only because I went down the tube path. 
Might look at setting up a full solid state system, in the future. 
The Parasound is a beautiful looking unit...
Cheers