The Living Prime Minsters

Seeing the photo of the living American Presidents gathered together for a fundraising event got me thinking what such a thing would look like if we got all the living former Prime Ministers together.
David Cameron stood next to Gordon Brown, Brown shoulder to shoulder with Tony Blair, Blair alongside John Major but it wouldn't work because the difference between the American Presidents and our Prime Ministers is all our leaders end their time as failures, removed from Office.
The British don't hold their former leaders with any respect, John Major suffered the worst electoral defeat by a ruling party since 1832, Blair rivals Thatcher as the most hated Premier and jumped before he was pushed, Brown resigned after losing the 2010 Election and Dave Cameron walked in a hissy fit over Brexit. 
The hapless Theresa May is deeply unpopular and just in place until her Party get it together enough to nudge her aside so we wouldn't be treated to photo's like the the happy, smiling faces of Obama, the Bush's and Jimmy Carter, it would be a grim line up of losers.
The difference is the Americans have a sensible two term rule while our Prime Ministers can keep going until they fall out of favour and are then removed by the electorate, their party or fall on their own sword.
The greatest advantage of a two term limit is they have a finishing line to focus the mind, knowledge that they have at most eight years to get things done and build their legacy and then someone else steps in.
Nothing would be left blowing in the wind for someone else to pick up the pieces like Thatcher did for Mayor when she was pushed out by her own party, Cameron did when he flounced out after Brexit or Blair who washed his hands over the Iraq debacle and left it for Brown to sort out.
Having a date to get things down by would make sure they were focused on getting things done sharpish but it wouldn't stop Prime Minsters doing a runner like Blair and Cameron when they make awful decisions and things go pear shaped for them, i'm not sure how you would stop that and in Blair's case, i'm not sure we would want to stop them going.