Showing the receipt buys you a year. By the end of that the employer is required to get the updated information.
A small excerpt form the USCIS Employer's handbook:
Reverification and Evidence of Status for Certain Categories
Lawful Permanent Residents
Employees who attest to being a lawful permanent resident in Section 1 of Form I-9 may choose to present a valid Form I-551, Permanent Resident Card, for Section 2 (or Section 3, if applicable). A lawful permanent resident is not required to do so, however, and instead may choose to present a List B and List C document combination, e.g., state-issued driver’s license and unrestricted Social Security card.
If an employee presents a Form I-551, you should know that Forms I-551 may contain no expiration date, a 10-year expiration date, or a two-year expiration date. Cards that expire in 10 years or not at all are issued to lawful permanent residents with no conditions on their status. Cards that expire in two years are issued to lawful permanent residents with conditions on their status. Conditional residents can lose their status if they fail to remove these conditions. Permanent Resident Cards with either an expiration date or no expiration date are List A documents that should not be reverified.
Lawful permanent residents and conditional residents may be issued temporary I-551 documents. These documents are acceptable for Form I-9 as follows:
1. . If an employee presents an expired Permanent Resident Card along with a Form I-797, Notice of Action, that indicates that the card is valid for an additional year, this combination is acceptable List C evidence of employment authorization for one year as indicated on Form I-797. At the end of the one-year period, you must reverify.
2. . If an employee presents a foreign passport with either a temporary I-551 stamp or I-551 printed notation on a machine-readable immigrant visa (MRIV), you must reverify when the stamp or MRIV expires, or one year after the issuance date if the stamp or MRIV does not contain an expiration date.
3. . If an employee presents the arrival portion of Form I-94/I-94A containing an unexpired temporary I-551 stamp and a photograph of the individual, this combination of documents is an acceptable List A receipt for the Permanent Resident Card. The employee must present his or her Permanent Resident Card to the employer no later than when the stamp expires, or one year after the issuance date of the Form I-94 if the stamp does not contain an expiration date.
NOTE: If USCIS has approved the employee’s application to adjust status to that of a lawful permanent resident, but the employee has not yet received his or her initial Form I-551, he or she can obtain temporary evidence of permanent resident status at a local USCIS field office. However, you may not accept Form I-797 that acknowledges receipt of an application for an initial Form I-551 because receipts for an application for a new document are acceptable only if the original document has been lost, stolen, or damaged.
