Thanks, James. I don't know why I had it stuck in my head that I had to have /PERSISTENT:no on a new line. It's working find for me now.
I'm not sure how you could get a timeout, but I know of a way to add a prompt. Use the
Install Express program (IExpress.exe in the system32 folder). It's pretty self-explanatory so just go through it, the only options you really need to change are to add a confirmation prompt and run the batch file as the installation program.
(Create new SED > Extract and Run command > Prompt's Title > Make sure you use a prompt!!!! > don't use a license > add batch file > the rest is up to you...)