pfSense 2.3.x uses OpenVPN 2.3.x. pfSense 2.4.x (still in Beta) uses the newest OpenVPN, 2.4.x, and I've found that key renegotiation is much faster and smoother in the 2.4 version of OpenVPN, so I can't wait until pfSense 2.4.0 is ready to ship.
At any rate, my thread was mostly about the Client configuration, but some directives apply to Server configuration as well. The most important directive to use is reneg-sec 0 to disable the timeout every 3600 seconds (1 hour). I've since disabled the reneg-bytes 1073741824 directive since it got to be annoying, since it still takes about 1 minute to renegotiate.
I'm not sure if remote-cert-tls server applies to a server configuration (in fact, it may not).
tl;dr: the most important directive to use is reneg-sec 0 to disable the key renegotiation timer.
Re: your question about having to re-issue OpenVPN installers to all employees: I doubt it. It really depends on what you have in the employee configuration files. reneg-sec 0 in the server config should disable it for the connection unless your client configs have some other number set in reneg-sec.