There are a number of bits of good advice that run contrary to popular concepts.
“Don’t be irreplaceable. If you can’t be replaced, you can’t be promoted.”
“If you do a job twice, it’s yours for life.”
More than a few people become tyrannized by their expertise. Often the only way to escape is to make a lateral move in the industry, and go someplace where your previous “specialty” is no longer an albatross around your neck.
And as I learned in the military, never volunteer. (Actually, I volunteered for two things while I was in. They both worked out to my favor, but I was very selective.)
I don’t EVER want to be “irreplacable.” It sounds so much like a dead-end job. ;o]