I've recently discovered soy milk and now keep it on hand at home but I have a few questions:

a) how long does it last once opened
is there a difference in taste between brands
c) how come it got a little clump at the top rim when I heated it up
d) can you use it as a substitute for regular milk

I like soy milk. I usually buy the Silk in the dairy case, either plain or vanilla lite. The Giant Nature's Promise label in the dairy case is ok too. I don't usually like aseptically packaged soymilks, but Westsoy froths well for cappuccino, and I keep small 3-packs of Edensoy Extra for soymilk emergencies. I have sampled a lot of soymilks and think the fresh Silk is the best. I always drink a carton within 2 weeks so I don't know how long it lasts beyond that. I think it is worth trying different brands because different people like different things, I know some folks who hate Silk. I don't use it in recipes, I use it in my coffee and my cereal mostly. I have cooked with soy milks in the past and they are more delicate and sweet than dairy milks--I hear Silk Unsweetened can work in creamy soups and whatnot though. My husband and I both get gassy from dairy but he prefers Lactaid milk to soy products and I use the Lactaid for bechamel, stovetop custards, etc.

My brother is Orthodox Jewish and as such keeps glatt Kosher. His dream is a fat burger with soy pepper jack and a big Soy Dream fake-ice-cream milkshake. There is some place near Chicago that sells this meal and he daydreams about it. Soy Dream is ok but I'd rather have dairy ice cream or a sorbet.

The one in the refrigerated section in the bottle - I forget the name - is gross. The stuff at the Chinese store is very vegetal - fine if you like that sort of thing - but probably not what you're looking for if you like Silk. But the Chinese stuff is essentially bean juice.

I don't know if it's the same gross clumping I get when I let it sit on the counter as when you heat it up, but my guess is that it's probably something to do with settling and how well it's emulsified. They definitely add a lot of stuff to what's in the grocery aisle to make it creamy and tasty.

I am pro soy milk is smoothies, tea and coffee. I really love the refrigerated coffee Silk (on sale now at Whole Foods!) because it tastes like a frappucino, but less guilt inducing.

Has anyone tried hemp milk? Apparently it's loaded with omega 3's and 6's (and probably 9's and 12's). I've been drinking the chocolate version with a little sparkling water mixed in. It's kinda like having a chocolate mallted. Unfortunately there is a little disclaimer on the side of the box that says "0.00% THC". Bummer...

Here are some answers:
a) I found 2 links that both say 5 days after opening and refrigeration: http://www.ochef.com/254.htm & http://www.wishh.org/whysoy/soymilk.html. However, it's been fine for a week to 10 days in my fridge.

2) There are differences in taste, also taking into account between flavors, such as vanilla, unsweetened, original and chocolate. Some, like EdenSoy, I think, puts sea salt in their soy milk. I really like Trader Joe's unsweetened, and one of my favorite ones is from the Tofu shop in Eden Center (they make it fresh daily, I think. The sweetened is the red cap, I think). It's not too sweet if you buy it from the tofu shop, but I found most soy milks from both the fridge and shelf sections (original flavor) are really too sweet, with about 6-8g sugar per serving.

c) I don't know the right word, but soy milk skin is what is produced. I think that occurs if you heat it at a high temperature. If you heat it on lower heat gradually, it won't have that effect. You can just skim that off.

d) I use it as a substitute in milk, milkshakes, cereal, bread making, ice cream making and almost any recipe that calls for milk. My mom made this alfredo-like sauce using soy milk and it was delicious!

I use part unsweetened soymilk, part skim milk in my morning cappuccino as part of my way of limiting but not eliminating carbs. My preference is Trader Joe's unsweetened in the light green aseptic carton, which is cheaper than Westsoy. Most refrigerated soymilks have sugar in them, which defeats my purpose. I don't use soymilk for much else, though my daughter sometimes likes soymilk on cereal. She also is very fond of chocolate hemp milk. She and Jonathan enjoy the aseptic packaged horchata (can't recall the brand) that I can sometimes find at the Takoma Park co-op or at Whole Foods. It is basically sweetened vanilla rice milk with cinnamon.

Unsweetened Silk is low in carbs. I can't drink it, just for coffee. To drink I like vanilla, although I prefer vanilla rice milk or almond milk.

I've pretty much given up on milk consumption outside of cooking. For cereal and smoothies, I use soymilk only, and I actually prefer the Trader Joe's brand vanilla soymilk to Silk.