Most pessimistic locking (check-out/check-in/cancel-check-out) scenarios must plan for the case where a client performs a check-out and then fails to ever either check-in or cancel the check-out. One way to handle this problem is for all clients to be able to track how long a document has been currently checked-out and if it exceeds a certain threshold, cancel the offending check-out and then perform its own check-out.
In CMIS, the PWC has a cmis:creationDate property which would seem to represent the date the PWC was created which is also the checked-out date. This date could be used to implement the scheme described above. In Nuxeo, however, the Live Document is the PWC and therefore its cmis:creationDate does not represent the check-out date. Would it be appropriate for Nuxeo to support the scheme described above by maintaining the checkedOutDate for the Live Document and exposing it as a nuxeo: schema property to CMIS clients?