I can spin up to 20mph and holding it with 64 gear inches. It took time but I got there. I can go faster, but thats when the spinning starts to get a little taxing but it's do able. I don't know your terrain, but here there are plenty of flats and rolling hills and climbs. My gear is also great in traffic because it's easy to get the bike up to speed. Traffic is my main reason for going so low, if there was none then I'd probably do 70 gear inches for street.

I'm not saying you need to go low like me and spin like 100+ all the time. Maybe you can try something in the middle, like 48x17. I think you current gear is an indication that you should work towards relying on your legs for speed and not your gear ratio, but that's just my opinion.