Only two musicians to remain members of Fleetwood Mac throughout the band's career:

Drummer Mick Fleetwood and bassist John McVie
Though Fleetwood Macís rhythm section may have provided the underpinnings of its name, Fleetwood and McVie held little sway over the direction of the bandís sound. Since its late-60ís inception as a hardcore UK blues duo, Fleetwood Mac changed line-ups-- and genres-- more times than care to be counted, with several of its members succumbing to mental illness or the allure of solo careers.
Source: All Music Guide, 1/1/1900