operating temp of stepper motors

I've not had the opportunity to run long jobs in the past but now
that I am beginning to run longer jobs I noticed that the stepper
motors run quite hot and wondered if this is normal. I measured the
case temp of my stepper motors measureing 150 degrees F. These are
23 sized motors wired in parallel at 4.1 amps.

Should I be worried about this temp or is this normal?

Ken