Setting political timelines is rarely a good move, IMO. If you don't succeed by your own estimates, people begin to wonder if you've bit off more than you can chew, and that's not a good position for a leader to be in. And of course there is also the opposition to consider. They may just decide to wait you out, and that's no good either, because that could like maybe they weren't the bad guys you painted them as being in the first place, since they aren't causing any trouble at all, and what on earth were you thinking! You can't win either way.
I agree that Desert Storm was beautifully handled by Bush1. General Schwarzkopf was disappointed that he wasn't permitted to advance further since they were already there, as I recall, but he obeyed orders and withdrew, and that was that. We never heard any further questions from him on that subject. Honorable man, and a good soldier.
I'll choose Assad over ISIS any day. I believe he has Syria's best interests at heart, and I like that. ISIS just wants to control the region, and they are showing their contempt for us by beheading our people which makes them brutal savages who shouldn't be in charge of anything, ever. I pity the people they would rule.