I'm a Sprint employee, and Product Ambassador for the Samsung Galaxy S10+
The week I received the S10+ I took it out for the weekend on a Boy Scout camp out with my family. As the title states, two days and overnight spent mostly in roaming. I didn't need to charge my phone once.
We were out with the troop in the outskirts of Wilson Kansas, basically in the middle of nowhere Kansas. (Look at the map of the US. If "Kansas" is centered, Wilson KS is a bit above the first "A".) Apparently there aren't many towers near the middle of nowhere Kansas. lol
When I realized my phone was roaming so much I got pretty nervous at first. There was no Wi-Fi, and if you're in roaming we all know cellphones will really try to connect your carrier’s cellular network, and can be a huge drain on the battery.
I had no travel charger but I also wanted to see what the device could do. After all, the battery is massive at 4100mAh. To put that into perspective if you had an older model like the S5, the battery in those devices were about 2800mAh. The battery in the S10+ is nearly 1.5 times larger. I had just gotten the phone, but I'd already moved all my apps and info over to it through Samsung Smart Switch. Plus I took advantage of all the extra storage, and added a few extra games. I was coming up from an S5 with 32GB of storage. So there were plenty of apps running in the background. Of course I took several photos of the landscape, the largest Czech Egg in the World located in Wilson KS, and several photos at the Eisenhower Presidential Library and Museum located in Abilene KS. All said and done and it still had 23% battery life. I was extremely impressed with the battery life. Saturday morning and day, throughout the night, all day Sunday, and didn't see a charger until Sunday evening close to midnight.