Every January I reset back to the typical default withholding and don't think about it till October. In October I take a close look at what I've withheld and what I'll likely owe, then I adjust for the rest of the year.
I get the best of both worlds. The government does not get an interest-free loan, and I basically get a 3-month "bonus" during the holiday season when people sometimes need more money anyway.
Stop getting those huge refunds, give yourself a 3-month pay-raise at the end of every year instead.
<ptp> how many emo kids does it take to change a lightbulb?
<Willy> HOW MANY?!
<ptp> none they just sit in the dark and cry