Interphase is the longest phase in the cell cycle, because, in that phase, the cell needs to grow, duplicate and replicate chromatin and other parts, and prepare itself for th â¦ e mitotic phases. Interphase has three stages, G1, S, and G2.n addition in some cases the cell does not need to undergo the full G1 or G2 phases such as in the early replication of zygotes. The actual longest phase of the cell cycle is what is called G0. This is the state the cell goes into where it is not preparing for the cell cycle. Most of your cells are in G0 right now.