First, your software works forever. So if you don't renew you can't get new versions, but you can continue to use the software as long as you like.

I think we send a reminder out after 11 months or so. It's up to you to go to our upgrade page to extend for the next year.

You can wait until you need to upgrade also. Most people do this. Just know we'll always be tempting you with new releases and features ;)

Some customers ask us to send them invoices yearly. We're happy to do this also.

It does not necessarily. You should check into buying the new seat by going to the upgrade page and put in your existing license(s). You can add a new license, and if the existing licenses were purchased with in 6 months, it will renew them for free. If after 6 months, it'll be 20%.