The old certificates aren't a huge concern moving forward because the new standards for trust libraries is requiring that all certificates not be trusted if the expiration is too far out. Chrome and most other browsers have already implemented these standards.

The real concern is the percentage of people using browsers that are no longer supported and therefore do not implement on the new standards like Internet Explorer. Microst really needs to stop caving to pressure and get rid of these ancient applications like paint.exe and internet explorer. That or just make new applications and give them the same names.