One consideration when downloading members from mainframe libraries is that the mainframe version could be updated, resulting in the use of an out-of-date version from a previously downloaded copy on the workstation. You could delete all downloaded copies as soon as the assembly completes on the workstation, but this would result in slow assemblies due to the frequency of downloads. A better solution is to periodically delete the downloaded copies. This could be done once a day or once an hour, depending on the frequency of updates performed on the mainframe. If you download members from each mainframe library into a separate workstation directory, you could delete the copies from each directory at a different frequency depending on the chance of updates in each corresponding mainframe library.
This problem is a good reason for having all project macro and copy members reside on the workstation. With the Tachyon assemblers, there may not be a need to have your project libraries on the mainframe, especially if one of the many excellent workstation oriented source code control systems are used.