Tough assignment -- by definition, hard cheeses = low moisture = longer aging. If you can go to 3 months, Asiago or Montasio might suit -- they are not super-hard, but certainly a thermo cheese that is cooked to a reasonably high temperature. That said, I think 3 months is on the low side for aging a Montasio. I just made my first Asiago a month ago, so I don't know yet how it will be at 3 months.