Without more information about what tax bracket you are in, I cannot make a recommendation about what your best option is, but here are a few things to consider:

 - You can still contribute to the HSA until April 15th of next year if you have not contributed your allowable maximum (for the current year that is the annual maximum / 12 * the number of months you were covered by a high-deductible plan).
 - Contributions to the HSA are pre-tax and will reduce your tax liability, if you are in a higher tax bracket, the money saved in taxes may outweigh the maintenance fee.
 - If the invested funds are returning better than inflation and the maintenance fees, it does not hurt you to leave the funds in place.
 - Though you may not currently have a high deductible plan available, the health insurance market is moving in that direction and you may find yourself back in a high deductible plan before too long. (I would wait at least until the next open enrollment to make my final decision.) The deductible that qualifies is currently $1250 single or $2500 family 
 - If there are any qualified expenses, you can use those funds without incurring further tax and maintenance fees. (For example if you could benefit from LASIK, that would be one way to empty the account.