"I'm really happy that we've been given the opportunity by HBO to run for as long as we have and to make a decision about when it felt right to us to conclude," she told PEOPLE. "It's really meaningful to not be wedged into anything but just to be able to let it take it's natural course. And that's super-awesome."
Dunham, 29, hit the presidential campaign trail for Hillary Clinton in New Hampshire on Friday, speaking to PEOPLE on the ride – in a Hillary for America minivan – from Portsmouth to Manchester.
Of course, the comedy Dunham created, directs, stars in and writes for still has plenty of time left: season 5 premieres Feb. 21, and the cast is preparing to film season 6, which will air in 2017.
"But I think when we get close to finishing shooting our next season, it's really going to start to be pretty emotional," she said.
Sadly, she thinks Clinton will be a little too busy working to become the first female leader of the free world to make Girls cameo.
When she series wraps, she says she looks forward to focusing on her feminist Lenny newsletter, making another movie and being "a human being with hobbies" – plus staying involved as a vocal political supporter.
"I'll continue to advocate for causes that feel meaningful to me and that I can be helpful with and turn my attention to," she said. "I'm really happy this primary is happening when I'm not shooting Girls and I have the opportunity to be out on the road and engaged in a way that I wouldn't if our show was already in production. Hopefully that will continue to allow me to do that."