Well, this is how I do it. I have a cutoff point for my bank account...$10,000. I let the cash accumulate every month until the end of the month. At the end of the month, I pay bills, the credit card, money into my 403(b), etc, and then everything I have over $10,000, I transfer to the Direct Loans people online. Then my balance is $10,000...and I start again...
Some months I pay them like $3500, others like $2000....but it winds up being about $2500 a month I send them. When my wife graduates, then I'll really start paying them down.
It works for me. It gives me a decent cushion if I need it and I am putting it down pretty fast.