The simple answer is that what you're proposing will never work (learn the difference between a tax credit and a tax deduction)
But, just to show you the math, assuming 8% interest on $10k you're looking at about $530 interest for 8 months
at a tax rate of 25% (federal only) you're saving $137
So the cost to you in delaying is $397
Not to mention, the maximum deduction for student loans is $2.5k and I'm pretty sure the interest on your $100k debt will be much greater than that
1. We are talking about the 10k I can repay, not the whole 100.
2. I am not trying to delay in order to accrue more interest; I am trying to delay so that the interest I pay will be deductible against income for that year.
Imagine that all 10k will be interest. And imagine that my marginal rate for 2012 would be 15%. If so, then the deduction would be worth 1500.
Now imagine I wait until 2014, when my marginal rate will (hopefully) be 36%. The deduction would then be worth 3600, which is 2100 more.
The interest on the loan for 1.5 years is 1200, so it would be worth it. This assumes that the entire 10k would be interest payment, and that I would be itemizing anyway in both years (is this an itemized deduction?)
This does not mean that one should borrow in order to get the deduction, since I need to pay interest on 100k in order to be in this position. I'm only talking about the marginal cost of letting the interest accrue further.
3. But, if you are correct that the maximum deduction is 2.5k a year, then perhaps I should pay only 2.5k this year, and save more for later. But, if I am going to pay 2.5k in 2014 anyway, that would not make sense. In which case, the problem is solved and I should pay it all now.