Our first recommendation would be to question if this is both desirable and feasible. Running simulations of extremely large schedules often generates a lot of “noise”. For example, it is almost impossible to run reliable sensitivity analysis, as the actual sensitivity of a project to any one activity will often be extremely low and it will be impossible to identify any key drivers in your schedule. Secondly, to run valid analyses, schedules must be of very high quality. Predecessor and successors for all activities must be correct such that the project can be updated automatically when activity durations change. Very large schedules are often maintained by multiple individuals and ensuring and maintaining a high quality schedule can be costly.
If you do decide to run a very large schedule, RiskyProject does have a few options that can simplify the process: Schedule Consolidation and Master Schedules.
Schedule Consolidation is a feature that will be available in version 7.1 that runs an algorithm on very large schedules and consolidates portions of the schedule that in effect minimizes the number of activities in the schedule while maintaining the validity of the analysis. This minimizes both the computer resources and time required to run a simulation.
In addition, using convergence monitoring, which will halt the simulation when continuing will not add any statistical significant value to the analysis and can speed up the process. Convergence monitoring Is located in the Schedule tab > Project Options > Calculation.