I did a 10 hour, 133mile gravel race (Funk Bottoms) with the 1040 Solar yesterday. I used Live Track, a Varia Rear Light/Radar, a HR monitor, PM, and wheel sensor. I had it in multiband-GPS mode and was following the GPS map of the course. Despite all of this, I had 78% battery remaining after 10 hours. I gained about 1hour 45min run time from solar charging.
Otherwise everything else seemed to work really well. The Stamina meter hit 0% around the 8 hour mark. I was definitely able to continue past this point, but similar to what DCRainmaker review said, at this point I had lost my top end and pretty much had to Z2 it to the finish. Impressive how closely the Stamina meter represented how I was feeling.