Is it acceptable to validate drying using an LOD spec target without regard to drying time? If so, does this mean significant time differences between batches would not be considered deviations?

Yes, it is acceptable to validate the process based on drying to a target LOD value. But you
should be concerned about extremely long drying times if you have seen any indication that the
product will degrade at elevated temperature or if such an extended drying time could cause a
problem with the API.