My take, funny but burns out too fast

So I watched this a few weeks ago. I laughed quite a bit in the first half of the movie, very funny and interesting how they only ever have the dialogue between the 2 characters. The problem is the 'gimmick' of having it be only the 2 of them is the humor burns out about halfway through and the last half could have been cut down in run time significantly and it would be more effective for it.