On the one hand, there are bands who, as soon as one of their members isn't suitable or doesn't meet expectations, are replaced, even if it's only when they can't play a song in the studio or when they're not up to touring. A perfect example would be a band like Kiss! Here, what counts is that the band keeps touring, keeps moving forward, no matter how or which members are in the band or have played on this or that song in the studio.
On the other hand, there are bands I'd call traditionalists who stay together, do everything together no matter what, they've got a career together, so they stay together. Here it doesn't matter how good the performances are, there's a kind of respect for all the members of the band, a loyalty, and that comes before the quality of what's on offer.
And I think Maiden is more in that second category. So, even though at the moment I admit I find it hard to even watch some of the clips on YouTube, because I can't help thinking about the last 30 years I've spent as a fan, seeing them on stage at the top of their game, seeing Steve or Bruce running and jumping around, Nicko with his power and legendary cool attitude, always smiling while playing almost effortless, I'm not sure a guy like Steve (or Rod?) is up to replace a member that has been in the band for more than 40 years..even if the quality is unfortunately no longer at the level it used to be...The irony with this is that Steve has said on many occasions that he would like Maiden to mainly be remembered as a great live band...