My Lennox natural gas furnace is about 20 years old and still working well except for the pilot light which now occasionally goes out. This first happened in January 05 and the thermocouple was replaced by a Sears tech. Now the same problem has started again.
After re-lighting it may stay on for days or weeks before going out again. Its not a problem to re-light but it will be if I am away from home for any length of time during the winter. Any ideas on what could be the cause?

Thermocouples are cheap,and cheap made,after 2 years its possible you need another,replace and keep an eye out . Don`t want the familey to get cold while gone over a under $10.00 part