A Workaround
I'm still hoping that someone will confirm this limit, but in the meantime I have implemented the following Work around. In fact it is more than a workaround since it allows a long list of sendtos to be broken into manageable pieces, and extended indefinitely.
1. Split the Sendto Directory into 2 parts. Sendto1 and Sendto2.
2. Add a shortcut in each one to a .bat file that will copy the other one to the Sendto directory after erasing Sendto. I named the shortcuts "A Load SendTo1" and "A Load SendTo2" so they will show at the top of the SendTo list.
Here is the bat I use for "A Load Sendto1" in SendTo2 ..just replace "John" with your username, and create a similar one for "A Load Sendto2" in SendTo1.
@echo off
:This Bat is used in SendTo2 to Load the Sendto1 Menu
erase C:\Users\John\AppData\Roaming\Microsoft\Windows\SendTo /Q > nul
copy C:\Users\John\AppData\Roaming\Microsoft\Windows\SendTo1 C:\Users\John\AppData\Roaming\Microsoft\Windows\SendTo > nul
Now SendTo will show this "Load ..." and if you select it the SendTo menu will be changed when you click on SendTo again.
This technique may be extended to Load as many different Sendtos as you wish.