I have absolutely no idea. But, surely, it would be over 1 minute. Remember - this is a buck driver. The IC itself isn't the hottest part on the board.
But feel free to buy one of these (the V2 version, of course) and test it out
Not really doing a test of it to see how long one could go, I did have a v2 1.7 amp version powered on with my power supply on a 4vdc test load for about two minutes and it didn't fluctuate at all in output. The board was hot after the test however.