Dull bits can be sharpened, as noted. However, technique is important to maintaining sharpness for a longer period.
I always drill at my press' lowest speed. I believe that's 650 rpm. In fact, because changing speeds is such a PIA on my press, it stays at that speed. High speeds will cause higher heat and may even render the bit totally useless.
Always pull the bit out frequently during a boring operation. Same reason as above.
Some will disagree but, I keep a can of "Dri-Lube" handy and spray the bit before starting the bore and, during the operation if it's a thick or especially hard piece of stock. The difference in the sound and in the pressure required is very noticeable.