no, there is not a more detailed tutorial for this.
first lets look at restricting number of downloads:
In the Orderdetail table, you will need to add a new column for the download count, set the default value to 0.
On the download_center.php page, you will need to add another condition to the where clause of the WADAorderdetails Recordset, lets say you want to limit the download to 5, and have named the download count column "downloadCount":
AND orderdetails.downloadCount <= 5
to update the counter, you will need to add an additional hidden form element to the download form, name it "prodID". Set it's value to use the ProductID column of the WADAorderdetails recordset.
Now in the Download file server behavior, check the option to update the download count.
Set the table to use the oredersetails table.
the key column to the DetailProductID.
Click the lightning bolt next to key column value and select the prodID hidden form element.
For the count Column select the downloadCount column.
You will want to make sure that the download file server behavior is before the WADAorderdetails recordset.
Now lets look at restriction by date:
Again you should add another column to the order details table for the expiration date.
at the time of order, you will need to calculate when the file download should expire, and update the store order details behavior to store the expiration date in that column.
you can then modify the WADAorderdetails recordset to ensure that the currant date is before the expiration date by adding another condition to the where clause.
AND orderdetails.expirationDate >= now()