Coding Lifetime Support, Membership ?'s

Hi!
I've been planning this for over a year now, and finally took the plunge and got everything up within hours last night (helps I'm a developer so I can do this with my eyes closed). I'm opening up a "Build your own Website" type of network using a WP Framework + Child Themes.

I have have ONE subscription level, with 3 options. Monthly, Yearly, or Lifetime. NO free levels, or users. After doing some research on this forum, it seems there are two ways to add lifetime support to this plugin;
A. By hacking code, which I'm cool with but don't want to have to do it again when you update your plugin. B. By using a membership system, which I'm cool with as long as I can still use Pro Sites?

Which is the preferred method? I'm happy to start using your membership plugin, but do I need it? I do not want to loose the way ProSites is setup, as it's precisely what I need for my business model.

Thoughts?

Nick