Long Range Flying Issues

[Rwy in Sight]

I understand that long range flying with or without relief crew has become an intergral part of the industry. Unfortunately I don't fly that much any more thus I have two questions:

1) When a relief crew is necessary and

2) What are the most important challenges and what do you enjoy most from a crew perspective for exemple boredom...

Thanks a lot in advance for your answers!


Rwy in Sight :O