Are you doing the Wurst Ride? It is really fun! Try this weekend to do another ride that is 45-50 miles. If you did 45 last weekend you should be pretty close. Maybe the next day this weekend you can do another shorter recovery ride of 20 or so. Just take your time and enjoy the metric, really I think you are probably already ready to go. 
ETA- Uh I just re-read your post. Yes, I think gradually trying a longer ride is a good way. Maybe not the structured "training plan" way but it is how I did it. Now I prefer 50-60 milers and have done centuries.
Last edited by Aggie_Ama; 10-30-2008 at 11:59 AM.
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan