CafeVelo

As a former soma dealer I know it doesn't work that way if you go through the dealer. They send a call tag and eat the shipping cost like any other company. Mine was gently used for a partial season, from June-September of last year. The package of fork+frame+good headset retails near $700 and I'm trying to dump it for around $450-$500

Carbonfiberboy 

Maybe you should reevaluate. If you're not planning on being near towns during the day or the evening, besides lots of water you'll need a tent and sleeping bag and lunch, dinner, and breakfast. If you want to use panniers for that, you'll want a proper steel touring bike with all the attachment points for racks and pannier. It's more than just fender eyelets. You'll also want the frame, fork, and brakes to have clearance for somewhat wider tires and fenders.

If you simply want to ride a road bike on long endurance rides, pick routes which have services. Simple. BTW when venturing into low water terrain, most LD riders use Camelbaks in addition to bottles. No need for 5 bottles. If you think you need more gear than will fit in an Arkel Randonneur bag (hard to believe), Carradice makes really huge saddle bags.

StanSeven

Right. For starters the geometry is much different. You already mentioned the taller head tube. Often the top tube is shorter and the wheelbase is longer. Part is from longer chainstays. Trail is usually different.

Many manufacturers do things with the actual frame to make them more girt able or use special sestposts.

Then there's the gearing and tires. Most have compaq crankset sets with side gearing. 28 are often the smallest tires that come with the bike.

McBTC

If you're looking at 105 or better components a new name brand comfort/endurance geo bike probably will probably come in a about $1.5K or less with an alloy frame and about $2K or less if CF... but, when you buy just the frame, almost like magic, the price of the frame alone is $2K or more...

superdex

guilty of americocentric assumptions. My apologies (turns out 'learnt' is used widely everywhere except the US. I learnt something

Shuffleman

Personally, I prefer the build out road myself. It can be fun and it can also be cheaper if you know where to find things and what you want. With that being said, the frame is always the hardest part for me. I like name brands, not generic ones for multiple reasons. I would consider Soma a name brand. As far as the warranty goes, I would not pay much attention to them. Most of them are not worth their salt. Despite all the horror stories out there, it is pretty rare that there is an issue with a frame. It happens and always will but it is not wide spread. I have only been riding the road for about 4-5 years but I have been a heavy mtb rider since the early 90's. I personally have owned multiple bikes and only broken one frame. It was a Specialized mtb and I cracked it jumping over oil barrels when I was a little more dense than I am now. I only had the bike for about 3 months and they would not honor the warranty. I did not blame them because I have to agree that I was being excessive in my use. In fact, I could not get my body to warranty the fractured scapula that I suffered in the same fall.
There are a ton of places to find great frames, you just have to be patient if you want to get the best deal.

dksix

LOL, I didn't know it was used outside of the South. Here is the mountains we are pretty country but I've been up in the coal country of WV and KY and I didn't even know what they were saying.

LesterOfPuppets

maybe you could 650b the venturi.

then get a stubby stem like the silver one in pic: