After rolling over a 401k you will no longer be able to retire the year you turn 55. Instead, you will have to wait until you are 59.5 years old. So, if you are planning to retire early you might want to keep your 401k where it is. Leaving it where it is isn’t necessarily bad...
maintaining the 401(k) plan gives you an option tobegin taking distributions prior to age 59½without penalty. If you rollover your 401k to an IRA or to a new employer’s 401k plan, this option is lost.