Based on these two observations, would you say that a cell spends most of its life cycle in interphase or in mitosis/cytokinesis?

A cell spends most of its life cycle in interphase

Explanation:

Cells generally spend most of their life cycles in the interphase phase.

A typical life cycle of a cell is divided into two main phases, which are;

The interphase represents a period between the last stage of one mitotic division and the beginning of another one while the m phase represents the mitosis itself. Typically, the interphase takes up about 91% of the entire cell cycle while the remaining part of the cycle, the active division/mitotic phase takes up the rest.