Until income growth (aggregate) stalls.

I doubt if we'll be able to hold out for long considering the scale of what's unfolding in the US. In 2000 the TSE didn't peak until about 6 months after NASDAQ began its tech meltdown, but the subprime debacle has already been brewing for a while.

The UK will be in for rough time when its real estate collapse begins. Housing there is far more over-valued than in the US, and the prospects for most people repaying their staggeringly large mortgages are about nil. Everyone is still in denial about it over there though.