Sandbox on a network share

I would like to place the sandbox on a network share. I set the THINSTALL_SANDBOX_DIR environment variable to
server\share\username. Most of our ThinApps are about 3 times slower in starting up and usage, compared to running a ThinApp with the environment variable THINSTALL_SANDBOX_DIR set to c:\temp.

Is it normal behaviour that a sandbox located on a network share makes the ThinApp about 3 times slower compared to locating the sandbox on a local drive? If not, please advise...