Two things to seriously look at after you have left the company:
1. Are the fees on the funds reasonable, and comparable to what you would have to pay if you moved the money to an IRA.
2. Is the company financially stable? If it is on shaky financial ground, I'd move the 401k funds to an IRA ASAP. If the company goes under,
the trustee of the 401k fund may go away, freezing the 401k for all participants until it is sorted out. Additionally, very high fees may start
being deducted from all accounts to cover the costs of the orphaned 401k plan. It's better to have moved your money out before this becomes an issue.