In the aerospace industry there is an old adage that says:
I think the same is true of Backpacking, but I would say in place of speed you can substitute durability. So, the limit of your ultralighting is often limited by your funds, except in the cases where durability does not matter.
Your existing KitTo lighten up, let's look at your existing kit. Examine each item you usually bring. It helps to have a list to help keep track of everything. Is there anything that can be removed or reduced? Do you really need 8 finger bandages in your First Aid Kit. One might think that it doesn't matter, those things are very light. However, when you look at each piece of gear make sure it serves a purpose to you in the backcountry, or it is just an extra burden. Do you really need a 6 inch knife with a folding spoon, a magnifying glass, and a fork?
Buy a scale!
Reasonably accurate scales sell on ebay for less than 20 USD. If you weigh every item you usually bring, you will be better able to make decisions on which items you should bring when two seem to be of equal value in terms of usablity and durability.
FoodExamine carefully what you pack for food, and how you pack it. Are you bringing high density food or things that make your pack needlessly large? I highly recommend purchasing a dehydrator. Not only will you save weight on your back, but you will also save money over the expensive store-bought offerings. Again, weigh your food and you will turn out lighter in the long run. If you can figure out how many oz. of a particular food item you need per person per day you can more accurately decide how much NOT to bring.
Some things on the market are reasonably inexpensive and go a long way to reduce weight. When I purchase gear I try to find things that are dual purpose. For example, in the winter I bring an MSR titanium spoon. It also serves as a wrench in case my snowshoes or crampons loosen while I am hiking. My friend was amazed when I pulled out my spoon and fixed his snowshoe while we were heading up to Mount Washington.
Just because something is lightweight does not mean that it has to be expensive. These days there are many alcohol stoves on the market that are both inexpensive and efficient. Because they lack some durability, you will find one stored inside my pot when it is traveling. Alcohol fuel is also more efficient at heating water per oz than the typical white gas or propane canister. As an added benefit, denatured alcohol can be used to disinfect. Some people even bring grain alcohol which has other medicinal properties! Typically these stoves work well down to 40 degrees, but after that you loose the ability to warm water in a short amount of time which is important in the colder months. My alcohol stoves usually stay home from September thru April.