We were thinking 40-50 days, at a minimum, to do Santa Fe to Glazier National Park. Though we were packing more gear than most and is not keen on doing 60+ miles a day on rough roads like the Divide.
There's not actually that much in the way of 'technical' off-road - most of the route is either gravel roads, Forestry Service roads (conditions of which seem to vary widely from state to state, with things seemingly getting worse as you head south!) with occasional bits of tarmac.
Read Paul Howard's book, "Eat, Sleep, Ride" (also available as "Two Wheels On My Wagon" for some odd reason) - one guy with very little off-road riding experience doing the Tour Divide in 27 days in 2009, a year noted for its particularly apocalyptic weather (rain, rain and more rain) and a higher dropout rate than usual. One guy he ended up riding with had barely any cycling experience
at all and the only thing that stopped him finishing was breaking his collarbone about 100 miles from the finish after an altercation with a pothole filled with sand.
I can also recommend Jill Homer's "Be Brave, Be Strong", which is a cracking read in its own right, again its about the 2009 race - life in general took a great, steaming dump on her so she decided to do the TD and took the women's record (since beaten by Esther Horanyi) largely out of sheer bloody-mindedness (admittedly, she had a bit of winter racing experience)
I have copies of both if you wish to borrow them.
This isn't the sort of thing you take on lightly - I've been refining kit and whatnot for the past year or so to the point where I've got the bike+kit weight down to sub-22kg (coincidentally the baggage allowance of the airline I plan to use
) and I've been ramping up the off-road distance accordingly, although training for anything like this is pretty difficult in the UK; the closest I can get is hooning round the fire roads at Dalby and Hamsterley with occasional forays onto the waymarked trails to keep my 'technical' mojo topped up.
Mike Hall evidently has this mantra written on the top-tube of his bike: "Nothing that's worth anything is ever easy" (
http://normallyaspiratedhuman.com/wp-content/uploads/2013/06/photo-7.jpg) - I agree 100%.