How long does interphase last?

The length of interphase (phases of mitotic division of a cell) can vary from organism to organism and cell to cell. 

Interphase includes a few stages: 

G1: this is the longest phase of the cycle. It follows the mitotic division, and is the part where new cells have the chance to start to growing. Proteins are created by the cell so that DNA can be replicated.  Usually takes about 10 hours. 

S: the length of this phase is unique to the quantity of DNA in that specific cell. This is where chromosomes and DNA are replicated and doubled. It usually takes between 5 and 6 hours to complete.

G2: this phase includes the first stage of mitosis. This is where most of the proteins needed for mitosis are created. It's the shortest of the three and usually takes between 3-4 hours. 

So in total, the entire interphase will last anywhere from 18-20 hours.