Don't worry about premature optimization.
You clearly have never worked with an old-school Assembly programmer. Yes, there are people who will drop an O(n^3) algorithm in without even realizing what they've done, and those people need to take up an exciting career in fast food preparation. But at the other extreme, there are also people who will count every clock cycle and hand-unroll the inner loop to minimize the constant factor of a rarely-used O(log n) operation.
Avoiding both of those is optimal in terms of the use of human time, and it really doesn't matter how many machines your code runs on. Sure, saving 32 milliseconds per user per day adds up to ten years of CPU time across a billion machines - So what? Your users don't notice that, but your development costs most certainly do.
FWIW, I would accuse myself (as an "old-school Assembly programmer") of needing to resist the urge to optimize, optimize, optimize everything - All too tempting, spending just a few more hours (that turns into a week or two) tightening up that one obviously-inefficient section of code; when in reality no one but me will ever know about it.