you don't need to skim all the time. i skim about 2 hours a day actually. i have no troubles at all. it's just a waste of electricity, and it will also remove the trace elements you just added to the water, which seems like nonsense to me.
if you turn your skimmer on and it is pulling scum like crazy, then you have issues that need to be addressed. i turn mine on and it pulls stuff for a while, then stops (this is the opportune time to shut it off IMO).
watch your tank and pay attention to it. you'll know what you need to do in a short time. check your parameters regularly, and you'll know when, and how much to skim. after all, you may feed alot more or less than me, or i may have a larger bio load than you, so, it's an individual thing, but all in all, i really don't think you can humanely stock a tank enough to warrant using a skimmer 24/7. :wink: