Not a trivial question! It's actually quite a common question we get.
You can capture as many Next Actions as you want to, on your context-sorted Next Actions lists, as long as they are all current, can be done simultaneously, and are not sequential or dependent on something else happening first. You just may not want to flood your Next Actions lists with all of that at once though. Really up to you. Some people like to stage it and just add a few at a time, staging the rest in Project Support.
I have a big project I am working on right now that will be done by the end of June. I have dozens of Next Actions captured on my lists to choose from at any time. Anything that's not on the list is a future/dependent/sequential or Someday action.
Does that help?
There's a Webinar I did with another coach, that's on GTD Connect, about project support, that you may want to check out too.