This isn't a place to coast and try to do the bare minimum. There are going to be contractual deadlines to meet and you may need to work hard to achieve them. This along with incidents and tech debt creates a certain level of stress. If you don't really care about the mission and the work you're doing, I think you're going to have a tough time. I haven't had to put in more than 40 hours a week very often, but it can be tough to find a good work-life balance since there's always more you could be doing and so many opportunities to do more.
They have been fair with vacation time. You can usually take at least 20-25 days a year and they provide a month-long sabbatical at 5 years. They have even given the entire eng org a day off after delivering a big project.
However, I'm not sure that if you're struggling with burnout that they will do as good of a job supporting you.