Look startups aren't perfect. You will most certainly work harder than at a large established firm. Your life balance will be no where near as good as at a large firm. But why are you electing to work at a startup? 1) You are getting some options and have the possibility of a big upside which does not exist at a large firm. 2) You want more responsibility and you will certainly get it in the form of wearing many hats…
To me they are large tech companies that have kept some sort of startup canon in place, and not in a good way.