I have a TF M750X but no longer ride it as it kills batteries. Was on the TF google forum everyday for the several years I rode it. We concluded on that forum that the TF regen (though stronger than E+ as stated here) was too strong for the batteries and played a role in killing packs prematurely. On top of the regen it seems large non-geared hub motors also have high draw especially at lower speeds and starting up as they have no gear advantage--this high draw also contributes to killing batteries (on all non geared hub motors) Thus I have this beautiful expensive upgraded Tidalforce machine that I cannot sell due to ethics because it kills batteries--I have thousands of dollars of dead packs from several years of use. 'Deerfencer' on the TF forum still rides his 750X and solved the problem buy using three packs in parallel to reduce the stress on the batteries.
Hopefully E+ has solved these issues.

Metalman--You could reduce the stress on your packs by wiring them in parallel so both packs are running together as deerfencer does. this way they both absorb half the amount of regen and must produce half as much power/draw and are cycled half as much--all these things give a battery longer life. How much was the extra hub and why did you need a hub--doesn't E+ offer a 'B' pack that is not in a hub??!!?