The longest stick's I've seen are the
Regal Tip Alex Van Halen signature series, close to 18".
I've found from jamming and practicing at home I don't much like sticks that are longer than average, I also don't like ones with larger tips and thick shoulders.
At the last 2 jam sessions I brought along my main sticks (Pro-Mark 747 Japan Oak) and for a couple of songs tried longer ones (Regal Tip and
Vic Firth) and some
Vater's with larger tips. Neither worked.
The longer ones slowed me down when doing very fast snare work and fills around the kit and I found the sticks would hit at times from the extra length. The larger tip ones felt out of balance, too front heavy and were only good for a solid, consistent loud rock groove as long as you didn't have to move around the kit much.
I found now that I have some experience I much prefer the standard 5A around 16" long with a tear drop or oval tip.