While a job certainly and reasonably means he'll have far less personal time, it is not an excuse to neglect you or your relationship entirely. Any job should provide enough balance for employees to maintain family relations.

Decide together what is a fair amount to expect out of the relationship once he starts working so you can both plan your workload and schedules to accommodate that much time of the relationship. If either one of you is unwilling or unable to meet this agree upon expectation, then you may have indeed reached a stage where you are no longer compatible.