Does ECU software wear out? If this really was a a software fault why has it not occurred during the last 3+ years of ownership?

Assuming you visited your local dealer, the same one charged me £50 to update the software on one of my ECU's to a cure stalling on startup problem. As expected it made no difference at all, and it needs to be booked back in to find and fix the real problem. Thankfully they refunded the £50 after I complained. But my issue was reproducible, where as yours has only occurred once.

If they ever advise me that my car requires a software update again, I will demand to see the software release note, to confirm the new software really fixes the issue that I've reported.

Cheers

Justin 
Gone - Range Rover Supercharged 2006

Fault code not on the invoice. I may ask for the details.

JustinP - sounds like it was the same dealer...