I've ridden about the same distance on my Giant FCR3500 that I bought in April, which is also pretty much a flat bar road bike, with bar ends. I have also ridden several metric centuries on it and just rode my first imperial century on it this week, but unlike you I won't be switching to a full road bike. Why? Because I've ridden a drop bar road bike before and I really don't like the posture of riding in the drops. I find that bar ends give me an aerodynamic enough position to cut through headwinds reasonably well, without forcing me to bend over as much as drop bars do.

And really, I just don't think that a full on road bike would give me many advantages over my hybrid. The roads here are pretty bumpy and I wouldn't want to be running any narrower tires than the 28s I've got on my bike now. Further, I don't think I'd get that much faster with a full road bike, as I can cruise relatively easily at over 30km/h on flat roads without a headwind.

Everybody is different, of course, but that's my $0.02.