I have iPAD 1 that started to be loaded with tweaks.
Now tweaks are not like regular applications, that go to sleep, when you move to another app.
Tweaks are utilities that needs to be on alert to serve us on any screen, any application.
To be alert and not to sleep, required some extra energy.
Energy on a computerized device is Clock cycles , processor power and Battery.
Truth is I didn't noticed a difference as of yet, but just wandering a giving my 2 cent thoughts.