A modern cycling GPS will last the entire ride, and probably several. Even touring all day it should last through the day without a charge. I have a Garmin Edge 820, which is as large as I am willing to put up there in the cockpit. But a 1030 is also a fantastic option if you don't mind having a larger device mounted. With its larger screen for mapping it would be a good choice for touring. The Edge 820 is adequate, but navigation isn't my primary use case for having it. Nevertheless it's great for helping me find reasonable routes to or from places I don't typically ride.
When I use my bike GPS the phone lasts as long as a phone can last when not in active use. When I need extra power I carry along an Anker 6200MAh battery bank. It's small enough to fit into my crowded saddle bag, and has enough power to charge my phone, with still enough left over to charge up a tail light and GPS, or headlight. If I need more than that, I probably also need a rest, myself, and wherever I take that rest I could plug in. But it's really never come to that for me.
So I'm in the "Get a bike GPS." camp. They're not cheap, but where a phone is pretty good at many things, a dedicated cycling GPS is optimized to be as good as possible at one thing.