[navane]

It's not premature if your crafting an office product in 2025 which sits in a direct line of 30 years of the same word processor.

[pradn]

It's premature in the sense that you need to care about it before you do profiling, which is the usual advice for perf improvements: "you don't know where the hotspots are, so write your code, profile it, and fix the slow bits".