Although I wouldn't go so far as to insist on switching brands (especially since, as another commenter pointed out, there has been so much consolidation, there remain only 3), I agree that replacing with at least a different model, or, failing that, a different batch, is a best practice for an already-built homogenous array.
Some of this can also be achieved ahead of time if one has multiple arrays with hot spares, by shuffling hot spares around, assuming there's some model diversity between the arrays but not within them.
I doubt I'll ever again have the luxury of being able to perform this kind of engineering, however. Even a minor increase in cost or cognitive/procedure complexity or a decrease in convenience just serves to encourage a "let's move everything to the cloud" reaction, so I keep my mouth shut.
Some of this can also be achieved ahead of time if one has multiple arrays with hot spares, by shuffling hot spares around, assuming there's some model diversity between the arrays but not within them.
I doubt I'll ever again have the luxury of being able to perform this kind of engineering, however. Even a minor increase in cost or cognitive/procedure complexity or a decrease in convenience just serves to encourage a "let's move everything to the cloud" reaction, so I keep my mouth shut.