If you are able to get a rate about 1% less and you have about $150K in outstanding loans, then it would take about 4 years to recoup the money spent on the refi. If you only have about $75K in loans, then it would take about 8 years to break even on the costs of the refi if only saving about 1%.
Of course, this all depends on the fees associated with the refi that you have to pay out.
I would just crunch the numbers and see what makes the most sense. Generally, if you can knock it down a solid point, then the refi is worth it in the long run.