For $250, I can download, install and use as much M$ software as I want??
Can I only use what I download/install only for the duration of time my TechNet account is active? Or, once I install the software, is it like I purchased a retail copy and I can use it indefinitely (and reinstall as required)?
You can download an .ISO for essentially any Microsoft business software, as long as there's no legal restriction on that software (Windows 2000 is no longer available, for example, because it shipped with Microsoft Java Virtual Machine).
There is a button you can click that will generate a product code for that software. Depending on the nature of that software, you might get one or two license codes, or you might get as many as 10. If you need more and you're a current Technet member, you call and ask for more, and they give you more codes.
The restrictions are that Technet is for personal or internal training or demonstration purposes only and technically you're only supposed to use the product keys while you have a valid sub. I've had a number of different sets of keys issues, since I have a number of different Technet/Academic Alliance/MS Partner Program IDs. Technet stuff is not for live deployment, not for resale. In practice, I have an apartment full of Windows Servers and a IMAP folder with pages of valid product keys for everything Microsoft has made since 1997.
Technet also offers a wider variety of available downloads compared to an Action Pack sub, I think.