Imran, First of all, welcome to community, and congrats on your ride.
Please do open an ownership thread sharing all your experience so far.
What ODO / month did you get the 2nd service done? 6 months / 10k kms?
If yes, then your 3rd service would be due at 12 months / 20k kms, whichever is early.
Nitrogen filling doesnt add to better FE. Its all a myth. It only keeps the tyre cooler, and tyre pressure doesnt reduce as quickly as regular air. SO you can check the pressure once in 3-4 weeks, and / or ahead of every long distance trip.