When making pasta, I often use small amounts of pasta water as an addition to sautes or to lengthen sauces. I have thought of saving more of the pasta water to refrigerate and use within 2 or 3 days, for say, a soup base or maybe as a light broth for cooking rice or bulgar wheat.  I'm wondering if anyone here does this, and if so, are the results worth the effort? I usually have a stock or other broth on hand but not always; so it occurred to me that leftover pasta water might have a second life.  Thanks.  A little more info - I got the idea from my well used copy of Lynne Rosetto Kasper's "The Italian Country Table" where in several recipes a small amount of pasta water is reserved for deglazing or cooking down within a vegetable dish. So, that's been my usage.   Consensus seems to be that it's not worth the effort to save for later.  
The major advantage of using pasta water is that it is high in starch rather than for any flavoring you may get from the water. You may find that you get some strange results if you're just subbing it directly for water or stock, and I wouldn't recommend keeping it for that reason.   Personally, it doesn't seem like it's worth the effort of keeping. If I want a thickening agent for a sauce or gravy, I'll just make a cornstarch slurry. However, you've just got a starchy water, so I'd think it'll keep for as long as tap water would (certainly 2-3 days if cooled properly).  