Old flex watt heat tape

Does this stuff get old and ware out? I have some on a metal rack that I got and some spots seem hot and some seem cold. I am having a heck of a time getting my temps stable. If I replace it should I replace my rack as well? I don't have a lot of money to put into a rack but I would like something that holds heat well and I can keep a stable temp. I am using 2 herp stat pros and each shelf has it own temp sensor.

Though I've never experienced flexwatt wearing out, I'm sure it happens after the course of several years. It sounds like you've got a good set-up, and flexwatt is cheap. I shouldn't think you will need to replace the rack unless there's something wrong with it.