The hearts will be somewhere in the middle- there should be a few jars– they will taste smoother and usually a bit sweeter than the heads and tails.
The first jars will be heads
middle jars will be hearts
the last jars will be tails
Let your taste buds decide-
How big is your still? 20 hours is a long time!! I usually run 10 gallons in about 8-10 hours depending on how fast I run.
I run my tails between 10-20% and save those and toss them into my still on the next run.
After 20 hours I would stop now as I would want to sleep!