I'll bump this.
West Orange Trail from Apopka-Vineland to Kilarney is prob my favorite stretch right here in Orlando. It's 14 miles one way, but you can continue on into Lake County on the Kilarney side (bring your legs for the hills once you cross the county line), or continue on the West Orange towards Apopka for another 10+ miles or so. This takes you through a rougher part of town in some places if you choose to head that way, so be aware of that.
I just did Cross Seminole on Sunday and enjoyed it, particularly once you get further out of town. Lots of cool bridges, including a big suspension one over Interstate 4.
I also enjoy the one that starts in Altamonte Springs, San Sebastian Trailhead and heads north, eventually connecting up with the Cross Seminole using the aforementioned suspension bridge. You could link these together for about 30 continuous miles, more if you are willing to hunt for the trail connection points a bit.
Now's a great time to be here, the weather is fantastic for biking. If you want more specifics on the trails mentioned above, just reply or PM me. Happy to provide input, factual or opinionated. :-)