Consistency is the score to watch
Over five minutes the consistency figure in your result tells you more than the WPM does. It is calculated from how much your per-second speed varies around its own average, so a score near 100 means a metronome, and a low score means you are alternating between bursts and stalls. Smoothing that out raises your real-world output more than chasing a higher peak ever will.
Posture over five minutes
Technique that is merely tolerable for a minute becomes a problem at five. Keep your forearms roughly level with the keyboard, wrists floating rather than resting, shoulders down, and the screen high enough that you are not looking down. If your hands ache before the clock runs out, that is a setup problem, not a fitness problem.
Building up to it
If five minutes feels punishing, work up through the three minute test for a week or two first. Stamina builds faster than raw speed, and it transfers directly — people who train at longer lengths usually find their one minute score rises on its own.