Female trio Expose' released 2 singles, before all members left (or were replaced) by the line up that would go on to have several US top 10 hits and a #1 , and are still performing together today.

hard rock band ratt now have no original members after singer and founder member Stephen percy quit. As far as im aware he aint been replaced and ratt have not toured since he left. Hopefully he will come back otherwise we will have another old rock band going round with no original members. Aint it time to pack in when your main man and last original member leaves?

If you take the word "bands" in it's true sense and not use it to reference singing groups, the original members of many bands which are still touring are probably dead.

And then, of course, you get the ludicrous situation of Bucks Fizz. One original member and he can use the name (which, ironically, is 'owned' by one of the 'new' members!). The other 3 original members have to perform under their own names, adding "formerly of Bucks Fizz". I know which line-up I would rather see!

The four-man group "The Drifters" have had 54 members. The line-up started changing a year after they were formed in 1953.

How many variations are currently in existence? I'm pretty sure there have been "american drifters" as well.

There's often splinter groups, because sometimes the original members don't own the name, or there's a legal wrangle over ownership. So you can get "The New," "The Original" or as you say "The American," prefix to a lot of familiar names of groups.

I like this line-up on a 45rpm record I have from 1973. Which I think may be, Rick Sheppard, Johnny Moore, Don Thomas and Bill Fredericks, although I'm not certain as there have been an awful lot of changes.

https://www.youtube.com/watch?v=i42Wuc_Pzoc

A lot of 90s Eurodance acts like Culture Beat and Cappella seem to tour Europe with absolutely no original members... it's very odd

The Eurodance acts are the best example of this. The producers of bands like Culture Beat Cappella 2 Unlimited etc etc own the rights to the name of the band and not the singers.

One of the biggest money spinners, is the stage musical "Jersey Boys," based on the life of Frankie Valli of the "Four Seasons."
The producers can put who they like in it and have as many touring shows as they please world wide, as not one artist is named in the publicity or show bills.

Yes, though 2 Unlimited have recently started using their name again