Internal temps

Is maintaining internal temperatures really that important. When I started brewing I thought I needed to have all the latest and greatest gadgets. I have an old kegarator that I use to ferment my beers in so I bought a temp controller and a probe that goes inside the carboy to maintain the internal temp. Is this overkill and a waste of money? Will my finished beer turn out just as good if I just regulate the inside of the kegarator instead? Thanks in advance for any input.

The thing is that the internal temp is necessarily going to be different from the external when there is a temperature change going on, either on the inside due to active fermentation, or the outside due to weather/ambient temperature changes.

During active fermentation, the internal temperature will be higher since fermentation is an exothermic process. When the weather changes, well...it's going to be higher or lower depending on the ambient temperature. I have found that if the external temperature is fairly static, that things tend to equalize over the course of 6-12 hours.

Since you most care about what the temperature is building up to and during active fermentation, and you only know the external temperature, if you just keep that a couple degrees cooler during active fermentation, or even just stick to the lower-middle of the fermentation range for that yeast, you should be fine.

I have a similiar setup.

Is 2 or 3 degress lower good enough to account for higher fermenting temps?