How Long Should Records Be Kept?

The HOA board I serve on recently received our community's records from the management company we had (we didn't renew our contract when the time came ...it's a long story). In these files were ballots from board elections held over the years, architectural change requests, violation letters, etc. What length of time should records be held, and what type of records should be kept in homeowners' files? I think any arch request should be in the files permanently, but some of the other items seem unimportant. Is there any kind of legal requirement for saving ballots?

Thanks