Add timer via OmniCC + 2 other small Questions

[hank]

Hey there,

i write an small Strength of Soul (+ slowimmun buff 4-piece pvp set) oUF Plugin but ive no idea how to add a Timer like OmniCC do for Actionbuttons - may u can help me there? (btw there IS a timer but i would be better to see this overlay u know?)

Code (3files):
http://pastebin.com/fxnH93Gd
(CreatePanel, CreateShadow and Point are Tukui functions btw)

and the other 2 small question that came in my mind:
1.
Does

do
   stuff
   stuff
   stuff
end

make any sense? I mean the "do" without something like "for .. do" ?
Cause i saw code like this many times.

2.
Does this makes sense:

f:RegisterEvent("PLAYER_ENTERING_WORLD")
f:SetScript("OnEvent", function()
  stuff
  f:UnregisterEvent("PLAYER_ENTERING_WORLD")
end)

PLAYER_ENTERING_WORLD only occurs 1 time after /rl, correct? So why should I unregister this event? It just get loaded again after the next /rl?

Thanks in advance
hank