If you leave your job before retirement age
What happens if you lose your job or change employers? Your active plan membership may end. If so, you will be entitled to a deferred or an immediate pension under your. You will also have the option of having the sums credited to your account transferred to a qualifying financial instrument of your choice.
Multi-employer plans
Are you a member of a pension plan in which several employers participate? If you leave your current employer and go to work or another employer who participates in the same plan, your active plan membership will not end and your benefits will continue to grow.
Note that...
When the plan administrator is informed that your active plan membership has ceased, he will have 60 days to send you a statement of cessation of active membership. The statement will indicate the value and nature of your benefits.
Other useful link