Use masking tape as a makeshift depth-stop guide when boring holes to the exact-same depth.
Measure up from the tip of the drill bit and wrap a piece of masking tape around the drill bit.
Align the bottom edge of the tape right at the desired distance from the end of the bit. And press together the ends of tape to form a short flag.
Now, chuck the bit into the drill and bore the hole. Slow down when the tape flag begins to sweep away the wood chips from around the hole.
Stop as soon as the surface is swept clean.
Repeat to drill more holes, which will all be the same depth.