My current SUL list is about 3.5 but this is only for minimalist solo outings and serious distance endeavours. If I'm trying for some personal record or I want to have the most minimal setup to focus on the experience of walking, I use that gear. Not shenanagins- that's a quilt, cuben pack, cuben poncho tarp, cuben bivy, cocoon jacket, camera, etc. but no stove. Some of the gear on my latest list is gear left to buy for summer but if I only add up what I currently have, it's still less than 4.
Everything beyond this varies a lot. When hiking with friends, I tend to carry 7-8 pounds (Tarptent, eVent jacket, downmat pad, quilt, cocoon top and bottom, alcohol stove, single ti kettle, good tequila, etc).
For winter, it's more like 12-15.
When carrying my son, it's a team effort and I carry about 35-40 pounds total. But that's food and my kid too- and he's getting heavier every day!
I really have two hobbies- gear and backpacking. I really enjoy the minimal side of backpacking- especially solo- and that's where SUL comes in. But when going for the enjoyment of backpacking with friends or family rather than a physical event, I put in what I want and don't weigh everything. These days, I know my gear well enough that the choices made are what's best for the trip, not a weight goal. The only gear list that I look at much is my SUL list and that's used on about 25% of my trips.
Great conversation. SUL is a certain focus at a certain time of year. But Backpacking is about experience, not scales. UL and SUL backpacking, after the gear is selected and packed, is about an enhanced experience and new possibilites due to less weight that you have to carry.