Hi jlnc. I'm in the same boat as you. I have a 2011 Trek FX 7.3 and I've been riding it just over 6 months, although not so much during the winter months. I'm already researching and looking around for a road bike. I'm reading Selene Yeager's book called "Every Woman's Guide to Cycling" and chapter 2 has EXCELLENT information and questions she asks to help guide you to what type of bike you'll want. Road bikes are typically categorized as "racing", "enthusiast" and "recreational". Even if you don't buy the book I suggest finding a copy and at least read that chapter. It's enlightening.
I took my Trek out to a totally flat island that's popular with all types of cyclists and did a 25 mile ride. I consider myself very fit and it was difficult and not optimally enjoyable for me, in part, due to the upright position. I felt like a sail catching a lot of wind. I also felt every vibration in the road. So, I think you could do a 25+ mile ride, but I think you'd be more comfortable on a road bike. One other thing to think about is how comfortable you'd be on drop handle bars. I used to ride a road bike for years, but that was 25 years ago, so for me, I realize that there will be a learning curve when I get a road bike. If you're proficient on a road bike already, then no worries.
Have fun exploring bikes.