Touring - Long Tour (90 Days) Training Plans?

I've searched here and elsewhere on the web and haven't found much in the way of training plans for long term tours. I plan on riding for about three months From St. Petersburg to Berlin south to Greece and then from Rome to Lisbon. I'll mix in some train shuttles so that I can cover the whole distance in the time that I have, but I would like to ride 40-60 miles per riding day spending 5-6 days on the bike per week. I'm in fairly good riding shape now, as I get in one or two 1.5-3 hour road or mtb rides per week mixed in with 2-3 other days of shorter rides or runs. I could start tomorrow and be ok, but I'd like to take advantage of the 2-3 months I have before I start to get in the best starting shape I can, while also being fresh and rested. I've trained for mtb racing before, but not the kind of long distance, day-to-day endurance I'd like to have for this adventure. On my previous longest tour of a week with no pre-training, my butt, hands and back were all in fairly rough shape by the end, averaging 50 miles/day, and my legs weren't too fresh either. I'd like to at least minimize this, and give me the option of going longer and faster as well.

I'd really appreciate it if anyone knows of any good web resource out there with training plans, or any personal suggestions. Thanks so much!

I do not have much to suggest but the best thing I did for my training was watch the weather and pick the days that had high winds and then head straight into them. I hated it at the time but it made winds in my tour easier to deal with.

Have a look over this website:
http://www.ultracycling.com/

And if there are any randonneuring clubs in your area which are still holding events, I'd recommend joining up with them. The club members can give you a lot of tips for riding a lot. Plus if any touring clubs in your area are running centuries, I'd also recommend building up and cycling them. They may also run some other day rides.

Gradually increase your weekend distance until you're comfortable doing things like back to back metrics (100 km/60 miles) and back to back imperial centuries (160 km/100 miles). If you're comfortable doing back to back centuries on the weekends, you'll know you can handle 40-60 miles a day. Do some of those metrics and centuries fully loaded as well so you know how your bicycle handles in those conditions. In fact, you might want to make a weekend of something like this as your shakedown ride ... ride 60-100 miles, camp, then ride 60-100 miles back home.

During the week, pick one day for a longer ride as well ... like maybe a 40 mile/65 km ride on a Wednesday. Then do shorter, faster rides on at least 2 more days. You will need a day or two off each week for rest.

You could quite conceivably be riding the distance you plan to ride on your tour now ... or soon, as you build up toward it.

The training plan I have used my last two cross country tours (3000miles and 4100miles) were 8 weeks each. I normally ride 100 miles each week so that is the base I have to work with. I only ride 5 days each training week and do something else physical the other two days.
Week 1&2: 150miles/week
Week 3&4: 200miles/week
Week 5&6: 250miles/week
Week 7&8: 300miles/week
This program gets me to the point that I can comfortably ride 60 miles each day. I have no designated breakdown of each week in terms of distance/pace each day. I make that up each week based on what I feel like. Most days are long and slow but usually one day is shorter and at a fast pace. The two rest days each week allow my middle aged body (64) to recover and minimize the risk of injury while training.
Just one more data point for you.

I have a training program similiar to "lighthorse" which has successfully toughened my body and mind enough to tour at 70-80 mi./day average for 1000-3000 mi. outings. There is no substitute for miles in the saddle. If I am heading into mountinous terrain I'll work out at home on a stairclimber as well to condition my achiles tendons and knees for the task. From your discription, you'll just need a little more time in the saddle before the trip and you'll do just fine....hope you have a great holiday....wish I could try a ride like the one you have planned!