Jamawani's experience is unquestionable and his advice good, but I think that it is at least a bit conservative with regard to mileage, especially considering that you are apparently fairly athletic. Also a lot depends on your touring style.
One example is whole notion of rest days. He mentions "only 5 days off for the entire trip" as if that was a pretty low number. I have not racked up the amount of touring miles that he has, but I have crossed the US a couple times with no zero mile days and without having any real desire to take any. I do take an easy day here and there, but definitely do not consider rest days a given.
On the TA we did take what was essentially a day off to go whitewater rafting, but even then we rode 8 miles down the road to our next camp. I have fairly rarely taken days off on other tours to do things but never really considered them rest days since I was generally active hiking or something. That was pretty much limited to a day at an especially day at a nice beach and adjacent hiking trails when I did the Pacific Coast and a week in the Yosemite Valley area hiking and sightseeing when in the Sierras.
I think the only actual "real" rest day I ever took was when I was very sick on my Santa Fe Trail trip and slept for 24 hours straight.
Lots of folks manage to average 80 miles per day (when I calculate an average I count all days). The Trans America is listed as being 4232 miles, at 80 mile days that is 7.5 weeks. It takes a 75 mile per day average to do it in 8 weeks. Whether you should do that much mileage is a different question, but it is certainly possible without superhuman effort.
Personally, if I were going to do the TA again I'd probably expect to finish in nine or ten weeks, but allow eleven weeks just in case. I am a reasonably fit mid 60s non athlete who carries a pretty light load due to a minimalist style of packing.
I agree 100% with Jamawani on the suggestion to pack light. Going no cook is a reasonable option, but even when I pack only 15 pounds or less base weight (including gear, clothing, and baggage, but not any food, fuel, or water) I still manage to carry minimal cooking gear. My cook set varies with the trip, but is almost always under a pound and sometimes well under (plus 12 ounces of fuel). Even if it is only instant oatmeal or Ramen noodles with tuna, a hot meal or even just a hot beverage can be pretty nice.
If interested in more details on my packing list decisions check out:http://www.crazyguyonabike.com/doc/Ultralight
There is probably some useful info there for most folks even though most will not want to take it as far as I do these days.