The article applies principles of scientific justification and methodology to effectively calculate the optimal frequency for inspections and vehicle maintenance schedules. The study analyzes outcomes, including identifying voyage cycles, measuring frequency variation effects, and the practical importance of conclusions. The study examines two key methods of predicting degradation. The first, the mean value method, focuses on calculating the average degradation value, considering all previous measurements. The second, the regression method, uses linear regression to make predictions based on the cumulative number of cycles. The frequency of measurements turned out to be a key factor affecting the accuracy of the prediction. Even minor changes in the frequency can lead to deviations in forecasts. If the frequency of measurements decreases, the risk of missed failures increases, especially at higher degradation levels. The method described in the article has the potential to be universally applied, which could extend its use beyond marine propulsion systems to other complex technical systems based on means of transport, including specialized rolling stock for automobile transport.