Watch thoughts / recommendations? I use a garmin forerunner 620, with an estimated active battery life of 8 hours.  From use, this seems like a high estimate

Coming up on my first 50 miler (Dirty German Endurance Fest) about 2 months from now, and I don't think the watch is going to last the whole run.  The course has multiple laps.  Should I swap out with my old forerunner 410 for a lap?

Are there better watches with a better battery life?