thermal expansion

I have some thermal expansion my pressure sits under 50 psi and never gets over 80 psi when heater is on and back down to 55 or 60 when it shuts off. One time I ran all the hot water out and let it heat up with out using the water and it only got to about 85 psi for about 5 minutes before it started back dwon to 60 psi should I worry?

I really dont want to install anything.

Thanks

You should be fine, if you have a constant pressure above 80 then a pressure reducer valve would be needed.