YOU should be doing this.

[Cellarbrau]

This is a super duper easy and totally free. There is no reason you shouldn't be doing it.

Take your sample for Original Gravity just after you pitch the yeast. After you take the reading, cover the sample with foil and ferment ~10 degrees higher than your primary temperature. Check it again in a week. Now you know the Final Gravity before your beer is even finished. No more guess work!

Once your primary reaches the FG you already determine you are ready to bottle.

 

[Veedo]

i have a hydro tube sitting on the counter bubbling away. it was an accident though, i forgot to check gravity before i pitched. kind of neat to watch!

 

[mikeysab]

It's called a satellite and there are people who do it. There are threads about it if you're interested in reading more about it.

 

[ndsgr]

I thought about it in the past, but fail to see the point.

 

[Dougie63]

unfortunately its inaccurate because of the volume size difference

 

[brushvalleybrewer]

I have heard that called a forced ferment test. Some discussion here.