+1 on making the load as light (and small) as possible. I've gone on a couple self-supported weekend trips with only a large pull behind trailer (no panniers). If I were going farther, I would certainly had slimmed down even more.

I used to do a bit of backpacking and fell in love with the products by "Big Agnes." www.bigagnes.com I have a number of their sleeping bags that fit over the air mattress. Each stuffs in a space about the size of a water bottle (probably can't literally put it in a water bottle cage, but..). These bags w/pads are incredibly comfortable for camping. Because I now tend to camp with the family, I have a 4 person tent that is quite heavy at around 10 pounds. It has lots of extra room. On the other hand, I also sometimes use a sub 5 pound 2 person backpacking tent. The 2 person tent packs up very small.

Likewise, depending on what your doing for food, I'd recommend a very light camp stove such as the MSR Whisperlight International http://www.campmor.com/outdoor/gear/Product___87723

Good luck, I would love to do some long distance touring in Europe. Maybe someday...