I would caution anyone on leaving a tourniquet up longer than 90minutes. At 90minutes nerve tissue is quite hypoxic and at risk for permanent injury. If you need to leave a tourniquet up for long periods of time you need to drop it every 90min for 5min to ensure adequate blood flow to distal tissue and nerves. Of course this has to be balanced with blood loss. In the case of profuse arterial bleeding that is a threat to your survival you will be trading your life for permanent neuropathy. The 90min rule is the standard of care in the surgical literature.