What percentage of a cell life is spent in prophase?

About 90% of mitosis is spent in prophase, however, mitosis is only 8% of the total cell life. Thus, a cell spends about 7% of it's life in prophase. The cell spends most of it's life in Interphase. Interphase is 90% of the cell's TOTAL life span.

To answer your question, the cell spends about 7% of it's life in prophase.