How long will low oil prices continue?

Enough to exhaust oil pricing hedges, enough to cause banks to tighten credit, enough to cause investors to seek greener pastures. The price drop will last until it gets the needed results.

Then after oil prices rise again, the banks and investors will likely not fund USA shale producers again because they know if they do, the Saudis will screw them again.

.. The Saudis have let everyone know that they will not tolerate high cost producers in the oil market.
They want to fiscally punish usa shale oil producers which is working well given the collapse in energy stock prices.

.. The Saudis have enough fiscal reserves to play this game for a few years even if oil drops to $20, they have publically stated this repeatedly.