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It is certainly to your corporation's legal benefit to be able to produce documentation showing that you had supplied all the protective equipment and procedures necessary according the SDS you had at the time.
In some cases, SDS's may be a part of your OSHA-mandated "employee exposure records" and you would have to retain these for at least 30 years.
For chemicals that were delivered after the HCS took effect but are no longer produced, you can try the distributor you purchased the material from or the manufacturer directly per the principle of "downstream flow".
In , you could get away with one sheet for the chemical if certain conditions are met.
See the OSHA Interpretation titled Hazard Communication Standard and Material Safety Data Sheets.
However, be sure to carefully check the revision dates on your sheets to make sure there haven't been any changes/updates that you might otherwise overlook!
And should you receive an updated sheet, then be sure to read the question, "Can I throw away old or outdated MSDS's?