What is the average lenth of a bottle exchange station? I'm talking about from the time one grabs a bottle, to the point at which it is still legal to throw one's empty. I'm practicing refilling my neverreach system, and I want to know if I'm hitting the mark.

I have never use the system you have - but bottles have worked fine for me.
Depends on the race, but a good guess would be 40-yards for the exchange area give or take.
I tend to enter the zone slowing to about 15 mph, pitch the empty (keeping one full bottle on board at all times) and with my cycle jersey zipped about 1/2 way I quickly grab 1 bottle of Gatorade and 1 bottle of water - stuffing them into my jersey. This technique allows me to focus on bike handling and other riders. I then get back to near race speed and grab the water drink some and dump some over me to keep cool. Then place the other bottle on the bike and get back to racing.

Good luck

Thanks! The neverreach system sits behind the saddle, with a tube that extends up between the handlebars. See: https://www.neverreach.com/page/page/276159.htm
It holds 64 ounces of fluid, so refills are not often necessary. I'm doing a 1/2 ironman in 2 wks, and one container will come close to fulfilling my needs. That said, one can refill by grabbing a bottle at the beginning of an aid station, empty it into the neverreach, and drop it at the end of the aid station. I'm slow, it takes me about 70 yards to get done, and if an aid station is 40 yards, I won't be able to drop in time.

sounds like you should use the neverreach as much as you can, and simply grab, sip, and chuck at the bottle stations...or use one cage to hold the extra bottle till the next station.

but i'm small, so i don't drink more than 60 oz on a 56. :/ refilling just sounds like it would mess up my whole race focus/cause me to crash spectacularly.

I use the NeverReach system and have run across the same problem. If the weather is hot, I will always go through 64+ oz in a half IM bike. I use a bottle cage to hold the empty. Alternatively (esp. if you are worried about the aerodynamics of a bottle cage), you can just put the empty bottle in the back pocket of your jersey (I doubt an empty bottle behind you will make any difference in aerodynamics but it might be uncomfortable if you are not used to it). I wouldn't suggest trying to refill the NeverReach in the aid station area (twisting around on your bike in a crowded section with wet pavement doesn't sound like a good plan to me).