Adalberto,
The CircleOS contains a power save management (Power handler), that automatically shutdowns the Primer in case of no activity during about 5 mn.
This management is scheduled (as other handlers) by the systick interrupt, so the delay has been cut off when you modified the systick period.
Modify the "shutdwon.c" (v3.7) or "power.c" (>v3.7) file if you want to deactivate it.
Remember that all the handlers of the CircleOS are scheduled by the systick IT, so modify it can lead to strange behaviors.
On the other hand, if you want to accelerate the application calls, you can use the "MENU_SetAppliDivider" ans set the value to 1, in order to call your application every systick.
Yves