The Ink Spots are an interesting case. They’re a vocal group from the 30s. Not only did that group Theseus itself and then dissolve by the 50s, but afterward there were legal disputes. A bunch of the past members claimed rights to the name. Courts ultimately said ‘nobody owns the name, you can all use it’. So anybody with any connection was going around performing as The Ink Spots, and those groups were also changing members. Over the decades there were probably multiple fully Theseus’d versions of the group going at the same time.

Andrew Hickey has a good podcast episode on it that you can listen to/read. https://500songs.com/podcast/the-ink-spots-thats-when-your-heartaches-begin/

A lot of k-pop boy/girl bands have rotating members that can age out and be replaced.

The Puerto Rican boy band Menudo from the 80s. Members are replaced once they hit puberty, Ricky Martin was one of its members. The group had 50 members in it’s lifetime.

Lynyrd Skynyrd’s last original member died in 2023 and they’re still touring.

The search results are interesting, but I haven’t heard of half the bands:

Bands with No Original Members

• Opeth: No original members remain, with the last, David Isberg, leaving in 1992.
• Jinjer: All founding members from their 2008 formation have left.
• Napalm Death: Formed in 1982, the band replaced its entire original lineup within the first five years.
• Molly Hatchet: None of the members from the 1978 original lineup or first album are present.
• Thin Lizzy: Still tours with no original members, including only two who played on earlier studio material.
• Blood, Sweat & Tears: Has had nearly 200 members, with all original members leaving early in their career.
• The Spinners: While they had long-term members, by 2010, the original lineup was gone.
• In Flames: No original members from their 1990 inception remain.
• Foreigner: Due to health issues, founding member Mick Jones ceased touring with them.
• Judas Priest: No original members are in the current touring lineup.
• Yes: Features no original members.

Bands with Only One Original Member Left (Often Considered “One-Member” Bands)

• AC/DC: Angus Young is the sole remaining original member, as of 2024.
• Iron Maiden: The only remaining original member is bassist Steve Harris.

Are there any original members of Ghost?