Nitrous or KERS

It's designed wrong then :P

In IGPManager this statement is true! See the IGP Rules.
but in Real Life KERS is charged over the first 3 laps. After that when a driver discharges the (batteries) KERS, it will recharge itself while braking. On circuits with alot of braking the batteries will recharge faster than circuits with less braking points.
That determines how "full" the KERS meter will be.
You can use KERS more times per race but it depends on the type of circuit how often.

I know. But here, you can fully discharge it only once per race, in longer or shorter bursts, but only once. It's a design by choice, not so hard to understand. Developers agreed it's more fun this way. And I kinda agree with them too, otherwise it will be the same advantage like in F1, almost all will use it in the same spots on circuit, lap by lap and no real advantage will be gain.

True ;)