A few quick points as to why I don't think this war is going to end very quickly:
 

1. Netanyahu hesitated about this war, hoped to avoid it, and accepted the terms of a ceasefire brokered by Egypt. Now that the IDF has gone in, the war psychology has changed.  I don't see the IDF stopping this incursion until it is able to negotiate a credible arrangement for the demilitarization of Hamas, which may mean a continued military presence in at least part of Gaza until that can be ensured. Israel is not going to  want to end this war in order to find that Hamas  can start again a week or month later to bomb Israeli cities again.
 

 
2. Hamas hasn't seriously contemplated a halt to this war. It doesn't care if its people are killed, it uses them as human shields, and it knows it can rely on Qatar, its financial backer, to write a cheque to cover the damage to its infrastructure. More and more the assessment here is that the only thing that may bring Hamas to the table is if it fears that the IDF is going to work not only to weaken it, but to re-occupy much of Gaza and/ or topple it. The IDF no doubt would want to put Fatah in place instead of Hamas, and it remains to be seen if this is possible.
 

3. Debka File has given an analysis July 21 which I agree with:
 
 "For the first time in its history with solid Arab backing from the Egyptian-Saudi-United Arab Emirates bloc. So determined are its members to obliterate the Muslim Brotherhood that they have virtually blacklisted Qatar for supporting the Brothers and for patronizing the Palestinian Hamas, regarded as the MB’s paramilitary arm.

"This rift has put a spoke in the diplomatic effort to set in motion effective mediation for a Gaza ceasefire predicated on co-opting Qatar.

"A bid to make Palestinian Authority chairman Mahmoud Abbas the bridge between the Egyptian-Saudi-UAE grouping and Qatar has likewise foundered. And there isn’t much Secretary Kerry can do if and when he comes over to try his hand.
 

US President Barack Obama’s suggestion, when he called Netanyahu Sunday, to build a new Gaza ceasefire around the 2012 formula concocted by the US, Egypt, Qatar and Turkey - and accepted by Israel and Hamas - for ending Operation Pillar of Defense, shows him to be cut off from the fundamentally altered diplomatic and military realities of the current Gaza conflict.
 

 
4. Jordan, too, knows that its own interests would be best served if Hamas were severely weakened, thereby weakening Hamas's chances of overtaking the West Bank, or helping to foment extremism in Jordan that would threaten King Hussein.
 

5. Iran's fingerprints are all over this Hamas -Israel conflict, which makes it all the more important for Hamas not to be strengthened but weakened substantially. (read Sayeh Hassan in  Toronto Star http://www.thestar.com/opinion/commentary/2014/07/19/irans_fingerprints_all_over_hamasisrael_conflict.html )
 

           
6. Retired Brigadier Gerneral Avigdor Kahalani who just raised $4 million told the Jerusalem Post the IDF must ignore international pressure and stay in Gaza until Hamas is “demilitarized.” He was one of the Generals that advised the IDF to go in. If you read what he is saying to the Jerusalem Post, it's clear this could be a long war--he uses the terms "many weeks" and "staying on the ground for as long as it takes."

“We’re going to find all the tunnels and destroy them, and the bunkers holding all their ammunition,” he said. “We don’t have a goal to stay in Gaza, but we have to protect Israel and create peace and quiet. Their goal is to destroy Israel, but we don’t have a spare country.”
 
With respect to an acceptable resolution to end the war, Kahalani said “only outside pressure can put an end to it,” citing Russian and American intervention via the United Nations.
 
“We would prefer to see outside supervision of Gaza, which would be good for all of us, including the Palestinians,” he said. “If UN forces can observe and control the area, and after two or three years they want peace with us, they can build their country and open their borders.”
 
Kahalani continued: “Otherwise [Prime Minister] Binyamin Netanyahu needs to stay on the ground for as long as it takes until the mission is accomplished.” [emphasis added]
 
Conceding that such a mission would likely take “many weeks,” [emphasis added] Kahalani said the IDF has no option other than destroying all of Hamas’s considerable arsenal.
 
http://www.jpost.com/Operation-Protective-Edge/Retired-brigadier-general-raises-4m-for-IDF-363602

7. Israeli radio reported yesterday that the IDF says it will take two more weeks for it to accomplish what it wants to in Gaza.

8.   A poll conducted by Israel Hayom on July 20 asked Israeli Jews if they supported or opposed Israel's ground incursion into Gaza. 80% supported it, 12% opposed it. 94% said they were satisfied with the Israel Defense Forces' performance thus far. 77% said Israel should not agree to a cease-fire with the situation as it currently is, with 16% supporting a cease-fire in current conditions. (Israel Hayom).