I have had my Firehawks on my 4C for the last 20k miles. Mostly highway with many spirited mountain drives.I put the Firehawks on my 500 Abarth. I really liked them and have been considering them for the 4C. When you say "happy", can you comment as to the grip, ride, etc.?
The rears are past the bars now, so its about time to replace. Plenty of life left on the fronts.
I will say that the rear grip has gone down significantly compared to new -- still feel confident on turn in, no confidence in the rear. Obviously the rear is useless in the rain now.
Ride is still pretty good to me, sidewall is a bit mushy compared to other tires.
As I'd like to say, 80% of the PSS / PS4S for 60% of the cost.