I also use Kerio Free...and that's just the way it is on my system...somewhere in the vicinity of 3 minutes before I can actively access anything.
I don't mind, since I don't speedtest my use of my computer...I never have understood those who want 30-second boot times
, but who don't care how sluggishly the system itself performs (because of malware and lack of maintenance) once it boots.
If the Kerio firewall makes you unhappy, it's not the only one available for free and which is effective. You might Comodo, ZA, etc. and see if they make you happier.