IMHO, the old posts should hang around, but should be set to read-only after a certain period of time, such as 6 months or 1 year. That forces new OPs to open a new question. I think this is a good idea because the new OP has different data and is running a different version of SAS from the original OP. Also, the new OP often has a slightly different question than the original OP.
I have seen old posts set to read-only in some other Q&A forums, so there is a precedent for this action.