Soffit Repair or Replace?

How do you know if a soffit is beyond repair? This is the worst one on the house and that bow makes me think it should be replaced. We used to replace these but it's been a while and I forgot how long it used to take us. I don't know that much about roofing/framing. How far apart are the rafters? Looks like the soffit is 6' long.

How long does it take to replace one?