I'm fermenting a porter, and pitched the yeast at about 75 on Sunday night (4 days ago). Lively fermentation started the next day, and though the wort had cooled to about 68 the first night, the fermentation brought it up to 72 - 74. There was 2 solid days of really active fermentation at this temperature. However, there's been a couple really cold nights, and now the CO2 bubbling out has slowed dramatically. The temperature got down to 65 yesterday, so I put a space heater near it, and it's now up to 76 - but the fermentation still seems really slow.
I'm wondering how the swing in temperature is going to affect it - any thoughts? Also, I'm going to be adding coffee and vanilla into secondary fermentation (in about another 4-5 days), how important is the controlling the temperature while in secondary?
Thanks for the help!