Interest rates are only going up. They weren't as low as 4 percent since like the 50s. I'm probably going to consolidate early and often.
And to clarify a correct point above, consolidation of multiple loans gives you the weighted average of the current rates on each loan, rounded up to the nearest (I think) eighth of a percent.
So if you have 10 K at 5 percent and 5 K at 10 percent, you'll consolidate 15 K at 6.75 percent. The advantage is that, if the original loans are variable rates, you've locked in current low rates.