@ atand,
No worries there as what lakambini has said. Lots before (same with me) had 5 or 10 year US visas and were still valid even if the passport, to which the valid visa is attached, has expired. That is why you will see travellers with a bunch of passports now.
I had a re-entry visa on my old passport, went for a vacation in the PH and renewed my passport. Upon re-entering, I presented my old passport to show the valid visa, and then explained I recently renewed my passport. Same should apply for your immigrant visa. It is the validity of the visa that counts, but alway remember, you should still have a valid passport in your possession when travelling, even if your valid visa is attached to an expired passport. Then you will need to present your valid visa (wherever it is attached to
) and valid passport at immigration.
And by the way - the new biometric passports is advised
not be stapled with old passports as the front and back covers now contain the RFID strip or ID strip containing the biometric info. You risk damaging that when you staple passports together. An alternative - use a rubber band
/cheers....