I bought an 11,000 pack nearly 5 years ago and it is as reliable as ever. I can get 4-5 full phone charges on that thing in one charge. If I'm going to the parks for anything more than a couple hours, I always toss it in my bag.For the same reason not everyone has sunscreen with them- not everyone knows how much they'll need it or remembers to bring it.
Personally, the last several times I've visited a theme park I've had a battery pack with me, since I use my smartphone as my only camera and tend to shoot a lot of pictures and video. The battery packs that Fuel Rod offers were acceptable in 2016 but are now far outstripped and outclassed by more recent packs from Anker and other companies. On my last trip I carried an 11,000 mAh pack that was just strong enough to get me through a full day of photos and other usage.