My cousins, aunts and uncles on my dad's side are mostly Mennonite, some Amish. They are not self-sufficient, and they've got 200-1000 acres, a coveted stall at a popular, well-traveled year-round farmer's market, and the means and know-how to be self-sufficient, if they wished to be in a pinch.
I've seen how they live. It isn't pleasant. I wouldn't want to.
I live in a farmhouse that was built in 1719. The ceilings are really low, as are doorways, and stairs are agonizingly narrow and rickety. Getting furniture up them was a feat of physics I still don't quite understand. The reason that our bedroom doors are so small I can bang my head (if I'm wearing heels--I'm 5'5") is because in 1719 in Massachusetts, people were so malnourished that they rarely grew to my height.
I'll never be self-sufficient. All I hope to achieve by eating as locally as possible and using the woodstove for heat (hey, at least mine is a modern one that has a good EPA rating) is to offset the expenses that oil inflicts on my budget. Often in New England, we get huge winter storms that blow the power out for days; my colleagues have showered and slept overnight more than once at work, because their houses had no power and no heat. I can always go home and have heat, food, and a lukewarm bath. This year, I've seen my grocery bills go up by $250/month, while my annual raise barely kept up with inflation. I'm already mostly vegetarian, so it's not a big dietary change for me to eat out of a garden.
My mother-in-law is about as close to self-sufficient as they come: There's no power lines or real roads to her farm, and she has only solar power. Where it breaks down for her, as for most people (including my Amish cousins) is textiles: growing, harvesting, preparing fiber for spinning, then spinning, dyeing, weaving/knitting the fiber, then cutting it and sewing it into a garment, uses a huge amount of time. It takes a lot more time to make a textile product than to make food. Making leather and making shoes out of the leather also takes a lot of time, although not as much as textiles. Both require fairly specialized tools. You have to have someone who does almost nothing but rett, spin, dye and weave/knit, all day long, in order to produce the most basic garments, sheets, blankets, towels, etc. for a household--which is why women used to make high-quality stuff for their "hope chest" and then use it the rest of their lives. At the rate I go through bluejeans, undies and socks, no maiden auntie could possibly keep up with me.
Don't get me wrong--every dollar I can wrench away from the greedy fingers of Saudi Arabia is a dollar I count as good for national security, good for the American economy, and good for the environment, and that's another reason I try to be a locavore. But my #1 reason is, I'm cheap.
However, there is one thing I would like to point out, Pat just reminded me of it, and last week there was some guy on NPR talking about something similar: Just because a method of generating heat/eating/getting around isn't 100% perfect doesn't mean that some choices aren't better than others. I think people sort of do this defensive, like, "It's hypocritical to ride a bike to work and say you're not polluting because it takes synthetic oil to grease the chain and the bike took energy and pollution to make the materials" and that sort of thing--well, yes, but a bike also pollutes less in the long run than an H2, so it's still a better choice environmentally. Yeah, woodstoves aren't pollution-free, but the modern ones are actually pretty good at exhausting minimal particulates with a sort of rebreather (Vermont Castings calls it a "secondary combustion chamber," it's a rebreather). If I was extremely clever and had more real estate, I'd pump the exhaust through a greenhouse, thereby filtering it further, as they do in Holland, so the potential exists there to mitigate the damage with existing technology, vs. waiting for the MIT geeks to think up something new. In the example of lead acid batteries, compare the lifespan of a fixed piece of equipment (battery) with the repeated exhaust and pollution associated with a coal plant, and normalize to existing recapture systems for pollution and reconditioning systems for fixed equipment...Most studies that compare the two don't really do this. Either they are crummy at math and accounting, or they aren't good engineers.
I digress. Anyway, no, I don't think I will ever be self-sufficient. I just want to have more disposable income.
I think it is good for the soul to participate in the basic processes of the world, like sowing and tending and reaping (and swearing at insects and groundhogs, that's an important basic process of the world too, right?) Practical benefits are nice, but frankly not usually all that large, unless you are spending a whale of a lot of time in the garden and barnyard.
