If you have a 20 year level term life insurance policy that has a level rate and coverage for a period of 20 years, your rate should remain the same for the rest of the 20 year term.
You can review your life insurance policy and check in the area explaining the rate for your coverage to find out how it works. Also, you may want to review the terms and conditions section to find out if you need to contact the insurance company if you change jobs and have a higher risk for your occupation.
However, since you locked-in the rate you have for a period of 20 years on your term life policy, it should remain the same.