Looking for Info from a Bit Older Riders

[Imdok]

I'm leaving Alaska in September of 2012 riding to Ushuaia then up to BA.
I may ship the bike to Capetown after that If I'm not too much of a wreck physically by that time (scheduling seven months).
The Alaska to San Diego mileage will be done in ten days as I've done this portion of the trip a number of times on H-D bikes over the years (at least from Fairbanks and Homer, AK, if not Deadhorse).

I'll be sixty years old by the start of the trip. I've done lots of long distance riding on H-Ds over the past thirty years but it's been a few years since my last long one (2005, 13,000 miles) and this trip will be done on a BMW R1200GS that I will ship north in a friend's Tracter-Trailer truck to Prudhoe Bay from Seattle.
I'll fly in on Alaska Airlines to Deadhorse.
I'm a big guy so that's why a R1200 rather than a KLR650 for me on this trip.

Any info from you bit older riders concerning being "on the road" south would be much appreciated.
Best place to buy "nappies", ect. (only joking, maybe Viagra?)
Curious as what you feel is a good daily range (I realize it's subjective, and depends on the roads and time schedule, if any, but what worked for you?)

Losing weight now and exercising more. Outfitting the bike starting in January. Wish it were an R1200GS Adventure model but price was right with low mileage and little use. It has the spoke wheels and BMW's three panniers.
Any suggestions from you older guys and gals would be appreciated.
A hearty thanks goes out to all of you whom have blogged the trip south, no matter what your age. It has helped immensly in preparation for the trip.
I don't plan on doing much hard-core dirt riding. I'm fine with fairly long distances on gravel roads though.

If anybody has any ideas as to making the R1200GS a bit more trip worthy please feel free to add your thoughts also. I probably wouldn't buy $1700 add-on fuel tanks but any ideas that don't go over about $2500 total would be appreciated (that's not including the costs of the personal and outfitting gear and spares). It has a good bash plate but I know it needs valve cover protectors and crash bars.
Thanks for any input.