If its gonna be just one driver - and a "comfortably mature" one at that, prolly oughtta figure on no more than 400-500 miles per day. Allowin' for stops, that works out to around 8 to 10 hours of drivin' at normal highway speeds. With 2 folks drivin', you can fairly comfortably cover about half again as much distance, drivin' 12 to 15 hours per day. I'd suggest a couple things - plan your overnight stops to put you on the destination side of any major city - you'll find your evenin' arrivals and early-mornin' starts relatively unaffected by rush hour traffic, and I think you'll find splittin' drivin' shifts into roughly 2½ - 3-hour segments doesn't wipe you out ... much more than that and fatigue sets in real quick - and is pretty hard to recover from. If there are 2 drivers, swap off, if there is only one, stop for a leg stretch, a bit of refreshment, and perhaps a brief nap (even just 10-15 minutes works wonders). Avoid really big meals durin' your travel time, and keep some energy foods and drinks handy in the car.
For route plannin', you might find it beneficial to lay out your itinerary usin' each of the "Big 3" online free map services:
MSN MapPoint ,
MapQuest , and
YahooMaps ; there will be minor variations. Set up an entire-trip map first, then break that into individual 2½ - 3-hour segments. A couple weeks or so before startin' off call the 800 number of the Travel Office of each state you'll be passin' through to get updates on contruction delays, detours, and the like, adjustin' your final route as appropriate, and plan your stops and make your motel reservations accordingly. Once you've got your travel plan figured, usin' any one of the mappin' apps print out detailed segment-by-segment "turn-by-turn" maps, and print out specific individual high-detail maps for each planned stop area, for each city you'll pass through, for each major highway interchange you'll traverse, and for any detour routin' as indicated by the varous state travel offices you'll have consulted. I've found it handy to print it out tablet style usin' the printer's 2-sided printin' option, assemblin' a route-order flip map for easy on-the-go reference.
Now, with the good advice outta the way, here's a tale you might get a kick outta:
One Lap of America.