This is effectively Spock's Beard's 5th "era", if every member change counts as an era.
1st: The Light
*Ryo joins*
2nd: Beware of Darkness to Snow
*Neal leaves, NDV takes over on vocals*
3rd: Feel Euphoria to X
*NDV leaves, Ted Leonard and Jimmy Keegan join*
4th: BNADS to The Oblivion Particle
*Jimmy leaves; NDV rejoins*
5th: Noise Floor to
I think SB fans, and maybe prog fans in general, just discuss SB's "Eras" in terms of who the lead singer is, much in the same way as Genesis was - Gabriel-Era and Collins-Era, and the one-off Wilson-Era. If you counted every line-up change for Genesis in the same way, then there were technically
11 line-ups of Genesis, but you only ever really hear of the 3 listed above.
Not every line-up change is an era, and not every era should reflect a line-up change. It's more based on the lead vocalist and possibly even the lead writer(s) of each era. With the first six SB albums, Neal was that voice and writer, but once he left, the writing duties were split up between the remaining 4 members and 2 co-writers, with Nick singing lead. When Nick left, his music did, too, so the writing fell on the remaining 3 members, with new input from Jimmy and Ted, the latter of which was now the lead voice of the band. And so with Noise Floor, we still continue the third era of SB with Ted still singing lead vocals.
Side-note - good god, could you imagine how many "eras" there would be for bands like King Crimson or Yes?! It'd be a headache...and in the case of Yes, would a similar line-up be considered part of that era, or something new? For example, the Keys To Ascension studio songs were written by the same band that did Tales From Topographic Oceans, Going For The One, and Tormato, but they're clearly not the same era, despite being the same line-up.
-Marc.