Long campaigns, Besides D&D and Pathfinder

[payn]

Traveller has a few. Secret of the Ancients, Pirates of Drinax, and Deepnight Revelation.

 

[pogre]

WFRP 2e also has The Thousand Thrones, which does not hold a candle to The Enemy Within, but qualifies.

Runequest has Griffin Mountain - old, but still holds up fairly well IMO.

 

[Tun Kai Poh]

Night Witches has a 33-mission main campaign (with a 6-mission alternate progression track) that takes the player characters from the founding of the 588th Regiment all the way to the end of WW2, in the skies over Berlin. I have only run 1/3 of it, but there's at least one podcast that's trying to get all the way through...

You can probably expect some attrition, as casualties are almost a certainty during the campaign.