the reserve entry in the CDU tells the FMC how much fuel you still want to have on board when you land. So in the ideal situation, this is the amount of fuel you will not use. if you set reserves to 95, you hardly have any fuel left for you flight.

If that's within the normal range, yes. Beware that range is dependant on weather, cruise altitude, cost index and payload...
But I already did 3000+ nm flights so...

Hi Manok.

I've done quite a few flights of around 3500nm in the 757-200 and landed with around 15,000lbs of fuel left. I often use a cost index of 0 - 20 so I get better fuel economy and longer range. The downside is that it will be slower flight.

On these flights I have usually set the reserve to about 5,000lbs of fuel. Even flying with real weather (Active Sky Advanced) and flying in a NNW direction and a headwind of around 25kts (corrected by the angle into the head wind) I still land with around 10,000lbs of fuel.

The range of the 757-200 is supposed to be 3,900nm and I believe I could get that distance with real weather permitting. My flights in the 757-300 have mostly been in the 2000nm - 2500nm distance which are well within its maximum range around 3400nm.

Mark