I'll grow up and move on. Eventually, manga will phase out of my life. Perhaps not entirely, but it's certainly not as important to me as it was five years ago. I used to stay on top of as many series as possible, but now I'm only keeping track of four: Naruto, Fairy Tail, Skip Beat!, and Kimi ni Todoke. Once those are over, I doubt I'm going to dive into another. I've got a boyfriend, and I'm working on completing my degree... Life will go on.
I understand how you feel. That is what happens to everybody: we find something we think is new, get into it passionately, passion gradually fades due to time and newer stuff looks inferior or a repeat of older stuff. IMO, when it happens, a nerd has two main options: grow out of his/her hobby, or try the older stuff that is regarded like classic.
I took the second option.
Back in my early teens I checked so many shows as I was capable to have my hands on. Manga, anime... whatever. However, time went on, and on my late teens-early twenties my passion had faded nearly altogether. I hardly found series enticed me or thrilled me. Nearly everything I stumbled into seemed a retread, dumb, weird -and not in a good way- or boring. Or -no thanks to Evangelion- a nonsensical mindscrew tried passing itself like deep.
In that time I temporarily stopped diving into anime and I started checking American comic-books that I liked when I was a kid but I had never got into (however that phase did not last long, either). However I found some few series kept my interest, like Naruto (it is funny. First time I heard about Naruto I laughed when some people called it the new Dragon Ball, and I paid no mind to it initially. It does not feel so long ago in spite of it has been nearly one decade and a half).
And then I started checking classic anime and manga shows. Of course, there are bad series, but also a lot of good stuff, and it reignited my passion for manga and anime (believe or not, it shows when a series created a trope instead of following it. It shows when something is/was fresh back then and when something is trite).
Like you say, life will go on. If you are growing out of it, then it is right quiting your hobby and moving on. I would still advice giving yourself a break, and then returning and checking some newer series, as well as classic stuff. Maybe you will find something you will enjoy as much as the shows got you into anime. It worked for me, after all.
Regarding me, when Naruto ends, it ends. I will find other anime show and will move on. I am not so into Naruto like I used back seven years ago, and I am already watching other anime shows, so it will be easy.
Personally I would rather Naruto ends up soon and Kishimoto does not make a sequel. It is never good to drag a show too long.