I think changing is more of a natural process than anything else. I don't think it's a matter of having to change in order to not get boring, it's something that just happens naturally to everybody. People just tend to change through time, I can say it for myself that I'm definitely not the same person I used to be 4 or 5 years ago.
Some things remain the same, of course, but generally most of the things change, especially when it comes to this transition from being a teenager and turning into an adult. Changes can be impressively huge through this time.
And that's how I perceive 'Now' - and this album for that matter - as a result from this process of changing they went through, from growing up, from having to live with a new band formation and all the stuff that have happened in the past years for them. I see it as a great and natural thing.
If they kept making the same kind of music for much longer, I'd probably start feeling it like pretty artificial, sell out music, cuz they'd know that a certain type of song works in the market so they wouldn't be leaving their comfort zone. I love how they took risks trying new things, because nobody is able to remain exactly the same for so long.