2 years in Bangalore. They are yet to open another service centre. But they have extended their serviceable area.
@Abhishek knows really well about being in this situation. His scooter had an issue quite far away from the Ather service centre when on a intercity weekend ride. He had to push his scooter into the edge of serviceable area for Ather to come and tow it for a service.
@akil333 another thing to keep in mind is
To not go for any early access beta programs of any sort 
it’s like multiplying your risk many fold.
If your house is JUST outside of chennai city. It’s unlikely that it’ll be covered in a new Ather centre. So they might just extend their serviceable area like they did in Bangalore. If its under 10Km from serviceable area. I recommend you go for it. The risk is not as big as the reward you get by owning a 450X. But anything more than that, it’s always going to be a risk.
@sachinshastry12 had to ship his scooter some 300Km because it had a known battery issue