Quite frequently? "Oh this operation turned out to take a while, I'll use pv instead of cat", or "oh what I grepped for wasn't in the current log, it's probably in the previous log that's gzipped, I'll replace 'cat current.log' with 'zcat previous.log'".
But how often do you make those kinds of changes in any of your scripts and not have to change anything? For me, exactly 0 times