What is the lergal posdition for two overlapping service bonds?

Tweet

A lecturer is deputed for higher education executing a bond that he will serve the College for 5 years after completion of his deputation period. He gets a degree, retuns back in time and his bond period starts. Then within a couple of months he gets selected for a higher post in the same College through selection committee while he is still under the bond of 5 years.Now for assuming duties of the higher post, he is required to execute anothe bond that he will serve in the new cadre for 5 years. The question is: Is it legal to consider that total bond period now is the remaining period of earlier bond plus new bond period? Or if he executes the second bond, the first one automatically is treated as null and void? Please clarify.