I probably have too many spares, but, you never know.
In the Pacific I had a Raymarine drive fail on a 10 day passage, but thanks to the Amel option of a second drive, the failure was solved with the flick of the A/B switch and we did not miss a beat.
As BeBe is crossing the Atlantic in January to complete our circle, I bought a spare course computer, rudder sensor and control head. Yesterday the original Raymarine course computer failed without notice while on a short sail in Malta. The control head read, "NO PILOT." After we anchored, I exhausted troubleshooting and replaced the course computer.
Now, I either need to buy another, or get this one repaired at a Raymarine depot.