OK. As far as anyone knows, there is no FICO scoring factor for Age of Oldest Credit Card. There is a scoring factor for Age of Oldest Account.
Because of that, I'd suggest you avoid paying off your student loan early, though paying the SL down is fine. Depending on the kind of SL and who the loan handler is, you may well be able to pay most of it off and then keep it open for a long time.
The one reason to keep your oldest credit card open is that CCs can typically be kept open for decades (as opposed to loans which cannot). So in practice your oldest credit card (properly kept open) will necessarily become your oldest account eventually -- for most people. (Corner case is someone who's oldest account is his mortgage which he is going to take another 25 years to pay off. That's the rare exception.)
Good news for you is that your oldest card (which you closed) was not too much older than the next (2.5 years older). If you can keep the SL open for at least a few more years, that will delay when the 7/2015 BOA card becomes your oldest account.
When people run into trouble is when they close their oldest account, and it was 15 years older (say) than their next oldest account. Ten years after they closed it, it drops off their report, and their "Age of Oldest Account" drops by 15 years, which is bad for their score.
