I like the current 30 seconds, because for almost all throws, we don't even need to keep track to know the player is in compliance. 15 would come into play too often. That might even slow down the game as play stops to argue about time or give out penalties.
Agree with the above for THAT reason. But again I contend that the "pace of play" could be sped up (in tournaments) if people concentrated on playing disc golf instead of "what ever else they seem to do to slow down play" and walked faster. Then they could take even longer than 30 seconds and the overall time to play would be less!