Frank Thompson wrote:

My wireless smoke/heat detector system is over 14 years old and I am
replacing the detectors for newer ones with more up to date
technologies. Should I also replace the keypad and the control panel
also?

Likely you will not find reliable, compatible detectors for that system
at reasonable cost. If it's wireless and not monitored, you should be
able to install a complete new system yourself. If you want remote
monitoring, you should have it installed by the monitoring company (or
their contractor/rep).