If I'm not mistaken, the only yarn in the Red Heart line with any wool in it is Heart & Sole-- and only yarns with a great deal, if not all, wool, will felt. But as for all other knitting-- Red Heart has some very nice, soft yarns for making everything else you can think of.
The "life" of acrylic yarn is pretty much eternity (although mind you, I haven't actually tested this theory out:-)). The only thing which will kill it is if it's in a damp place and develops mold and mildew, or if it's stored in such a manner that the skeins rub against each other, which will create pilling and fluffing.
As for amounts-- a 3 oz skein of worsted weight will make you a pair of mittens or a hat, or probably a good deal of small toy patterns, and 2 of those skeins will get you a scarf. For an adult sweater you will need several skeins-- the way to tell is to look at the type of yarn (there is a weight number within a drawing of a skein where the info is on the label, from 0 - 6). Then you need to match that up to the pattern you want to use and look at the required ounces or yardage. Let's say the pattern is for a yarn "4", which is worsted weight, by the way, and a lot of the Red Heart yarn falls into this category. It tells you you need 28 ounces for the item. You need to find a yarn which is a "4". Let's say that yarn comes in 3 oz skeins. You need to buy 10 to make that sweater. Now, let's say you're looking at a pattern which just gives the name of a specific yarn, but no number. Look up the yarn on line and somewhere you'll find out its weight number.