It appears that Opty is correct in that the re-exam doesn't stop, nor does an expired patent prevent subsequent re-exams.

III. AMENDMENT AFTER THE PATENT HAS EXPIRED

Pursuant to 37 CFR 1.530(j), "[n]o amendment may be proposed for entry in an expired patent." Thus, if a patent expires during the pendency of a reexamination proceeding for a patent, all amendments to the patent claims and all claims added during the proceeding are withdrawn. This is carried out by placing a diagonal line across all amended and new claims (and text added to the specification) residing in the amendment papers. The patent owner should be notified of this in the next Office action. The Office action will hold the amendments to be improper, and state that all subsequent reexamination will be on the basis of the unamended patent claims. This procedure is necessary since no amendments will be incorporated into the patent by a certificate after the expiration of the patent.

37 CFR 1.530(j) further states that "[m]oreover, no amendment, other than the cancellation of claims, will be incorporated into the patent by a certificate issued after the expiration of the patent."

Thus, at the time the NIRC is to be issued, the examiner should ensure that all rejected and objected to claims are canceled. The examiner should issue an examiner's amendment canceling any such claims not already canceled.

The cancellation of the original patent claims is the only "amendatory" change permitted in an expired patent.

emphases by me, corrections welcome

http://www.uspto.gov/web/offices/pac/mpep/documents/2200_2250.htm