Specific Gravity Question

My question is in regards to the time it takes for fermentation and the initial gravity. If you have a high intial gravity is this a good indicator that the fermentation process will take longer. A recent brew I had a low intial gravity and took less than a week to ferment. Fermentation looked strong. Since a way to know when fermentation is done is measuring when it hits final gravity it would make sense the larger the difference between intial and final the longer fermentation will take.

NOPE it ain't like that, fermentation takes as long as it wants, it's a factor of the brew, the yeast, the temp, airation pitching rate and loads of other stuff. In my opinion fermentation will NEVER be complete in a week. My rule of thumb is three weeks then have a check and leave it another week to make sure, this process will give you better beer.

All other things equal (yeast strain, temp, wort sugar composition...), a low OG wort will usually finish faster than a high OG wort, especially if there is a big difference in OG's between the worts in question.

For a 1.040 to finish in a week, that doesn't surprise me. 4-5 days of fermentation and few days for the yeast to clean up and start dropping out is not unheard of for light brews, people do that sort of schedule with BierMuncher's Centennial Blonde and then keg it - they go from grain to glass in 2 weeks, sometimes a little less.

Usually higher OG beers take a little longer to finish (there is more sugar to eat) and benefit from some additional conditioning time. If you don't control your temperatures, these can still finish very fast, but flavor suffers.

Now, if you aren't controlling your temps or pitching the right amount of yeast, it may not be the best beer in the end. One reason for fermentation to progress really quickly is temps that are too high, and that is pretty common for new brewers. Best things to focus on when you are just getting started are: sanitation, pitch rate, temp control, and patience.