Plugin Update Clarification

Hi Team,

First, let me say that my experience with WPMU DEV has been just excellent ~ your support and responsiveness are unbelievable!

So a question about plugins/upgrading, etc.: I am not a developer, will be using the plugins only for my own project. I'm a bit unclear as to the upgrading available with plugins I purchase ~ for routine WordPress compatibility updates, the kind that just keep the plugins running as WP evolves, will I need to maintain a monthly membership?

In the Terms it seems that we can use them "forever", but without updates, eventually they'll become out of date and buggy. Or maybe I'm just becoming buggy-eyed. (Had a lot on my plate lately, apologies if this was an obtuse question.)

Thanks so much in advance!

Lisa Elin