Thanks! This has been helpful if not what I hoped to hear.
My company varies the amount they reimburse each semester depending on how they're doing financially at the time (some is tuition benefit, some is money that would otherwise go towards my bonus). It's ranged from $1500 to $5000, and averages $2800. This semester it was only $2000, and it seems like they've trended lower over time.
If I refinanced, the loan amount would be very close to what I pay now.
Just for kicks after reading your responses, I did some math with an amortization calculator, and it looks like being able to graduate/refinance earlier would save me about $2500 in interest over the life of the loan (making payments equal to $525), plus get me about $2500 in interest subsidies (over the 20 months until I'd graduate, not a year like I calculated earlier). That would be $5k savings for $8.4k in cost. Still not worth it.
I'll try throwing more cash at this as I have it, and just continue to be patient. If my company reimburses me more than about $2500 a semester I'll take two classes, but otherwise stick to one.