I am indeed also a homebrewer, just finished bottling my 2nd batch. I enjoy cooking, and very much enjoy craft beer, so it was always something I wanted to do, and getting a homebrew starter kit for Christmas really got me going. The first batch (an unintentionally low-gravity extract E/APA) was better than I expected, and was a great learning process. My 2nd batch (a partial mash dunkelweizen) has great potential thus far.
I washed the yeast from my most recent batch, and am planning on doing this from now on, as it's so easy and saves $3-7 per batch.
I don't pretend to believe that I save any money homebrewing, especially considering I now drink far more beer than I used to. I'm looking forward to the day when I will go all-grain (partially for cost savings, partially for flavor and control), but need to save up for a down payment to move out of our cramped duplex first, so the fiance says no new equipment until we get a house. I am OK with this.
As for the overcarbonation problem, probably too much/ unevenly distributed priming sugar. How do you prime your bottles?
Shelf life depends. A typical beer should be drank within 3-6 months. Homebrew should probably be drank quicker, as the processes used in homebrewing lead to much quicker oxidation/staling reactions than those produced commercially (that being said, many brewers have discovered beers sitting around after a year or so and found it tastes phenomenal, so YMMV). Very hoppy beers should be drank quickly, as they lose their fresh hop flavor over time. Strong beers (> 8% ABV) can age longer, a year or 2 or more, and probably should be to give the flavors time to meld.