Ves did not actually have to invest much time in order to set up his ambitious Mental Simulation Training System.
Vulcan had already begun to use his formidable expertise and capabilities to build it up from scratch. By borrowing Ves' expertise as well as the knowledge that he had absorbed from his growing number of 'associates', the spiritual incarnation achieved incredible progress in a short amount of time.
In fact, Vulcan's ability to construct the MSTS was so impressive that Ves even contemplated the possibility of outsourcing future work assignments to his incarnation!
The difference in productivity between the two was too great. Ves was still bound by mortal limitations while Vulcan was much less constrained in this sense.
Of course, Vulcan was not capable of replacing Ves entirely.