I have a backup G70. Bought used at a great price (once upon a time, people were almost giving them away! LOL)...
But as I use that one keyboard for EVERYTHING, it made sense. I had a PCB failure in the early days of my G70, but fortunately I coaxed it to work for a week, while my local store I bought the G70 got spares. Turned out they couldn't really find what was wrong locally, so Roland sent ALL replacement boards for it, and the tech replaced out the lot just to make sure it was all good.
Even did that under warranty (which was only a week or so from running out!) and all I had to pay was the bench fee. Awesome service, Roland!
But it was a wakeup call for a backup...
Now I am transitioning to the BK-9, I'll probably sell one of the G70's and get another BK-9. If you base your ENTIRE show around one piece of gear, especially one that few stores stock, it pays to have a backup. I do keep recordings of all my songs on MP3's and CD's, should something go wrong on a gig, but so far, so good.
Plus, it's nice to have one in the house for playing around on, rehearsal and working out new stuff, while the other sits in the car ready to go... Just grab the USB stick and go!
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An arranger is just a tool. What matters is what you build with it..!