If you buy Pro & want updates, you have to check with the LW site to see if updates are available & then download them.

Email support is available if & when it's needed during the 6 month period by going to
http://www.limewire.com/english/content/support.shtml
& clicking the 'get support by email' link.

It's up to the user to save & back up their Pro installers (just as you would for other programs, in case the computer crashes etc)...once you've downloaded a Pro installer & saved it it's yours to use forever if you like
But...after the 6 months has elapsed you'll no longer be able to download free Pro updates. If you decline the offer of the new subscription at a discount, you'll have to buy Pro all over again if you decide you want to update later.

So it is a one time payment, but you pay once for any installers you might download & any support you might get during the 6 month period.