Rodwha, have you checked out the articles and gear lists on the home page of this site, left hand column
? Lots of good info there about lightening the pack. When I started lightening up (mandatory due to age and a bum knee--the alternative was to give up backpacking altogether), the 27-lb, 7-day pack list was my model. No, I didn't use the same brands or models of gear (except sleeping bag), but I took Packlite's weights as a guide. By now I'm down to 23-24 lbs. total pack weight for a 7-day solo trip (in the high Cascades 3 season or Rockies 1 1/2 season). That includes camera and fishing gear (items usually omitted from lightweight gear lists, even, oddly, when photos of the trip that include fish are included). A solo overnighter for me would be about 15 lbs. That includes everything I need for comfort and safety, including full tent (I hate bugs) big enough for me and the dog I no longer have, and a nice cushy insulated air pad to cushion my old arthritic bones. Also plenty of insulation, since I get cold easily.
Where the weight adds up is when you're packing with young children, for whom you absolutely have to take a full change of clothing, kids of course being strongly attracted to water and mud, to say nothing of food spills. I discovered last summer that it's a lot more fun when the grandkids reach teen years and can actually carry part of the food and shared gear.
A few assumptions in my achieving my weight include backpacking in places with frequent water sources so I rarely have to carry more than a liter at the time (water is heavy!). I mentioned on another thread that I may have to carry more water at a time this coming summer, which promises to be disastrously dry. Two liters (4 lbs) would be the max for me. A gallon (8 lbs.) of water, the minimum for a day in the desert, is an awful lot of weight! That's why I backpack in the mountains!
Compare your list with Packlite's. I personally found this process quite an eye opener (my previous weekend pack was just under 40 lbs, too much for me to carry). The articles are really helpful, too, although I'd ignore his advice to cut off labels. The labels from several articles of clothing didn't even register on my postage scale (to the nearest 0.1 ounce), and I lost fabric content, size and laundry info that I later wanted. A lot of the lightening up process includes finding items to leave behind because not needed, or finding multiple use items. Going light doesn't have to mean self-sacrifice.
I doubt you'd ever want to go much more than a week (maybe 10 days at the most) without resupply. I know I don't--makes the pack heavier than I can carry! Resupply normally involves a trip to a nearby town including a laundromat and a place with a shower. Otherwise I just rinse socks daily and do a quick sponge-off in the tent at bedtime (unless it's too cold). My change of (relatively) clean clothes stays in the car, along with moist towlettes to clean up with, to wear on the way home. Once you get away from the trailheads, everyone else out there is dirty and smelly too, so you'll fit right in!
In towns along the long trails you'll see thru-hikers in laundromats wearing their rain gear while washing their clothes. You'll also find that, except for a few areas where towns are really far apart, they rarely go more than a week without resupply, and more often no more than 4-5 days. If you're interested in that sort of hiking, try reading some thru-hiker journals on Trail Journals or Postholer.