Q. What about the engine life of FZ FI?

Don't worry about engine's life, it's one of the best in its class, the only thing is how you are maintaining it, if you are maintaining it good then it will never let you down. Few basic things you need to take care of, timely oil change, proper gear shifting, timely change of oil filter, cleaning of air filter, on long drives maintain speed under 85 KMPH (since it's a air cooled engine so it may get overheated) etc.

I think I will last life long, just that you should keep changing the engine oil oil filter in the petrol tank, lubricate the chain sprocket and grease and over oil, and wash the bike once in a month

Superb engine, arguably the best in the class.Though life of engine of any vehicle depends on so many factors viz. driving, road conditions, fuel quality, regular servicing & maintenance etc.