Rosko, Eldred, Hi! Suggest you go to http://www.ultramarathonrunning.com/training/ and look up some 50-mile training programmes to see how you're doing - an easy one to follow (from my experience) is http://www.trailrunevents.com/ul/schedule-50m.asp (Ultraladies 50 mile schedule), which uses a "two weeks hard, one weekeasy" approach. There's also a good schedule for training for races about this length (40 miles to 100K) in Bryon Powell's book "Relentless Forward Progress", reaching a peak at 51 miles per week.
Before my first 50 in August I worked up to e.g. 30+12 and a few weeks over 50 miles per week. I've got Thames Trot 50 in just over a week and I've not managed as much running, due to injury, but I did manage 30 +10 last Sunday/Monday (with the 30 in snow reaching 4 inches deep), so I'm feeling I should be okay so long as my injured ankle holds out...
Don't forget you're allowed to walk during the long runs - I use "walk the uphills", mostly, although some people use e.g. "run 25 mins, walk five" - it's getting lots of "time on feet" that's important, not speed.
Psychologically, I find it good to either set myself a long run over part of the course of the race I'll be doing (so for NDW50 I did one run which was the first half, another which was the second half), or to have a long loop or out-and-back such that you know you're heading for home now! - that can make the last few miles easier.
And don't forget to practice eating and drinking while you run/walk, and carrying your foot/water/emergency clothing with you - the day of your race shouldn't be the first time you wear your backpack!
And don't forget to take time to look around you while you're out on the trails, and enjoy it!