Games with hundreds of planets are not normal, and can last a very long time. I've never played a game with that many planets, so I can't tell you how long it should take, but my longest game was a 100 planet game with 5 stars and 5 AI's (all enemies) which lasted seven hours.
A lot can affect the length of a game. The layout of the map, the way your enemies behave, and just a random stroke of luck can greatly change the time the game takes to play out. In a 1v1 game on a small single-star system, matches can last 30-60 minutes. On larger maps it can go accordingly longer. On big maps, 6 hours isn't uncommon, but longer than that is an oddity. However, as I said games with hundreds of planets are not normal to begin with.
A small map usually has 5 colonizable planets per player, a medium one has 10, and large ones have 20. Your map has 60 planets per player, easily putting it in the gargantuan (ie, off the charts) category. Maps that big become a giant game of cat and mouse, because there's just so many planets and only so many units to form your fleet. That can take a long time to resolve.
