Yep, when the programing of new fob is successful, it feels like a mass weight being removed from my shoulders. If I loose my only key & fob, I think the cost to get a new key & fob will be very costly (including recovery truck to get my zed from wherever it's parked at that time to Nissan dealership)
Yeah it could be a real nightmare losing your only key.
When I had my Imported Impreza that only came with one key which always worried me so I tried to get a new key cut from a Subaru blank key. It was a nightmare.
The first key the key cutter did wouldn't turn to start the car and then got stuck in my ignition barrel. After 20 minutes in a car park swearing & wriggling the key I finally got it out so went back to tell him it didn't work.
He then cut me another key which again I went back to my car to try.
This second attempt was better but still wouldn't turn in the ignition barrel to allow me to start the car although I did manage to get it in & out easily enough. Went back to the key cutter again & tbh told him straight that I wasn't doing that again as he obviously couldn't cut me a key that worked.
In the end only having one key though for the Impreza was the easiest of my problems with that car as it was a never ending story of drive, mod, repair, engine blow up, repair, drive, gearbox destroy itself etc etc.