Thanks Jarkko. But no dice - typing into psql for 7.3.3 gives this error:
Unable to identify an operator '+' for types 'timestamptz' and 'integer'
You will have to retype this query using an explicit cast
physworx=# Unable to identify an operator '+' for types 'timestamptz' and 'integer'
Could this be related to the changes in timestamp from 7.2 to 7.3?