I set a Schedule Constraint of 24 months. Why does the Solution Panel show a 22-month schedule for the life cycle?

There are several reasons this could be happening, but the most likely cause is that you entered a target probability of more than 50% for the Schedule constraint. For example, if you enter a time constraint of 24 months at a target probability of 90%, you are asking SLIM-Estimate to calculate a risk-buffered solution that provides a 90% probability that the project will not exceed 24 months: in effect, a risk-buffered solution.

The difference between the expected solution of 22 months (50%) and your constraint of 24 months (90%) represents the built-in risk buffer that protects you against possible size growth, lower than estimated productivity, staff availability issues, or other facts that may affect the delivery date. The size of this risk buffer is determined by the uncertainty range around the estimated size, PI, and manpower buildup.  The Solution Panel always displays the 50% solution because it is the work plan.

If you want your solution to correspond exactly to your input constraint values, use desired probabilities of 50% for those constraints.