I think most full time jobs, after you've been there a longer period of time, allows you to stash enough vacay to get a month. Growing up, my dad has regularly been able to take off 2 consecutive months every 2 years with the company he worked for 30 years (starting at about 10 years into working with the company).
I will be taking 3 1/2 weeks off into my 3rd year with my company this spring
Now if they are paying for a month long break, in addition to you keeping your vacation time, that's pretty awesome. In European countries, a month every year is normal....it's sad that it gets us so excited here in the US. LOL
I like the RV/NPs idea. I don't know where you live, but I would fly out furthest away from your home, then rent an RV and drive through back (to save time). Unless you prefer to do a circular trip and see more parks. 1 month will fly fast though, especially if you are staying a couple nights per park. Whatever you decide, have fun!