10 years to E-7 isn't too bad ... it's possible if you're a sharp troop and in an MOS that has competitive standards/qualifications. A lot depends here on whether the promotion points were low enough for E-5 and E-6 to get promoted quickly after your promotion board.
If you take a lot of college courses in your off-duty time and all of the correspondence courses that your MOS offers, you will have an excellent chance of getting selected at 10.
12 or 13 to E-7 is probably about normal. If you haven't made E-7 by 15 or so, I'd say that it was probably too late to hope for promotion.