I tried to kick-start a starter last week. It was w1084 Irish yeast with a production date back in September. I threw it in 1/2 gal of 1.040 wort. I set it down in the basement 65F and gave it a good shake. I came back to it the next day and gave it another shake. No hiss, no fizz, nothing. I shook it a few more times in the next couple of days and no hiss, no fizz, I just wanted to wait it out before taking a gravity reading. The fifth day, I shook it and it hissed and fizzed like crazy. I opened the lid and smelled it. The yeast was infected. I made the starter too big with yeast too old. I also had it in the basement in an adjacent room to sauerkraut that I'm making. Step up your starters and try to get them fed within a few months of the production date.