Training to ride the TransAm from Yorktown, Va to Florence, Oregon [View all]

[peacebird]

We'll depart the end of April. We are currently riding our trainers indoors for 45 minutes each day during the week and doing outdoor rides on the weekend (when weather allows). Today was a two hour jaunt up to Afton mountain in 36degree temps. We added a couple miles over last weekend and managed it in the same time, despite the much colder temps.
We are adding 15 minutes to our long outdoor ride each week, looking forward to when it is light early enough to get our daily training ride outside because the roads out here are hilly and hard.
Anyone have any ideas on training or cross training we should be trying?
We hope to ride 50 miles a day, our current weekend ride is about 19.
Thanks!