Hot water heater stays lit for 5 days or maybe 3hrs I can relight it OK but won't stay lit.

Time to change the thermocouple, see the image below, Thanks.

John

How old is the water heater. Im betting you have a combustion air problem. Could be dirty combustion air screens, or plugged anti explostion device. I suggest calling Bradford White's tech support number with your model and serial number and have them walk you through the steps to take. Most newer water heaters are a bit more involved than the old ones, and simply replacing the thermocouple is more of a job than it used to be, and many times does not cure the issue.