SOP is in fact pairs of aircraft on CAP doing shifts, usually in the order of 4-6 hours per shift. If all you're doing is 'loitering' flying a fighter isn't actually that tiring. Especially something as sophisticated as a Typhoon. Assuming they're half smart they'll also have more pilots than planes, so it'll end up no harder than a normal days work for each one.
In fact I tend to agree. It's security theatre. The bare fact is nobody is going to try to crash an airliner into the olympic stadium - the security measures instituted since, well, the obvious reasons, make it pretty much impossible to hijack a jet these days. There's an ever so slight possibility a suicide bomber could get on board one and blow it up over London but there's nothing an EFT nor ground to air missile installation can do about that.
As RB suggests, the prime targets for terrorist attack aren't in fact the 'marquee' venues, it's the outliers and peripheral locations where almost by definition security will be laxer and in some cases impossible. Take the last time we did this kind of thing as an example - the IRA didn't try to blow up one of the stadiums in Euro '96, it tried to blow up the city centre of one of the venue cities before the game was due to kick off. You can't secure the whole of London, nor would it be practical to try.
Jon
