As far as I understood the normal procedure is like this: first time you send it in they clean the sensor. Second time they change the shutter and if the problem still persists after that, you might get a new D610. Of course I can’t guarantee this, some people got lucky, other didn’t. For some they just repeatedly cleaned the sensor.
As for the weight: this is a personal thing. Befor buying a FF camera I used my cam mostly for travel, family and social stuff (parties, meeting friends etc.). The D40 I had before was perfect for this, but when I upgraded I fell for the FF meme. When I had my D600 I took fewer pictures than before.
It was too heavy (for me) to carry for a full day of travel photography, so I left it in the hotel. It was too big to easily take it to a restaurant for pictures etc. the advent of useful Smartphone cameras made a DSLR for this kind of photography superfluous in addition. Mind you, it also depends on the lenses you use. A 2.8 Zoom will always be bigger than a small prime. But even though I had a lot of lenses (24, 35, 50, 85, 105 primes, and a few zooms), I decided to switch to MFT, which was the perfect middle ground for me.
Now I know how this board reacts to MFT so I’ll just say that you need to decide for yourself what is import for you: image quality, pricing, gear weight etc.
In this pic you can see my three different cameras, and the difference in size. The D600 with its lens is around 3x the weight of the EM10 + lens. Of course they are different lenses, but you get the general Idea.