Reduce screen refresh rate

**Is your feature request related to a problem? Please describe.**
With `ui.fps = 0` the screen supposed to refresh only when there're changes.
However, it still refreshes quite often, which may reduce a lifetime of a screen.

**Describe the solution you'd like**
I suspect uptime counter is the problem, as it may force screen to refresh on seconds change.

If there is an option to disable it - it may reduce refresh rate.