question about fermentation

[gone]

okay, so sometimes your beer starts fermenting within hours of adding yeast. other times, it could take three days or more.

my question, is there any downside to a very slow fermentation other than the waiting? will it have any negative or noticeable effects on the finished product?

 

[Arneba28]

A long lag time will obviously increase your risk of it getting an infection before fermentation starts. I tend to always ferment on the low end of the spectrum for most of my batches to minimize ester production. Beers that ferment out fast will still need the same aging time as those the blow through fermentation.
Chances are if they are fermenting super fast, your temps might be to high. But if it fits the style it may still turn out ok. I once fermented an irish stout in the mid 80's, it finished up in 36 hours but tasted horrid.