Solution
One possible solution could be to use a Functional Global Variable (FGV) design pattern. This implementation computes the time difference, in each iteration, between the elapsed time and the initial time. When this difference is equal or greater than the target time, the VI stops.
However, FGVs are used as SubVI, therefore you have to implement a main VI that executes the FGV, as can be in the following image.
Please see the attach zipped file for how the above example is implemented.
The control Required Time is in seconds, therefore, if you are using hours you should perform the following conversion:
Hours = Seconds × 60 × 60