If on gravity, you should move right or left 2-3" and up or down 6". Which ever you go, right or left, always go that way on every tree. If on vacuum, drill on the opposite side of the tree, in year 3 drill half way between year 1 and year 2 old tap holes counter clockwise from hole #2, , then yr 4, opposite yr 3. From there you go back to yr 1 hole and drill halfway between #1 and #3. Continue this pattern always trying to be as far away from the most recent holes as possible. While some use some sort of marker to ID holes, most just look for the old scars, they will show for many years in the bark.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.