I think you ought to keep what you have. I left one on for 4 hrs and it never worked again.

: After a 9-day break, I went to work on my latest strip-built
: project and discovered the glue gun still on. Amazingly although
: the glue was a little brown, it came out just fine. I can't
: believe it didn't start a fire or just burn out and quit
: heating. I am going to look for a gun with a timer on it.