That is equivalent to asking, "how long is a piece of string?!"

It depends entirely upon the capacity of the 9V battery, and the power consumption of your circuit.

However, if it's a PP3-size 9V battery (the small "rectanguar" one), and your LCD alone is taking 60mA, I'd say you're doing OK to get 1.5 hours.

Is there any particular reason why you're using a 9V battery?
Does anything in your system actually require 9V?