Maximum SPM is still useful
It is a comparable hardware specification and a ceiling. Official current commercial examples publish maximum speeds around 1,000–1,500 SPM.
Real designs rarely live at the ceiling
Acceleration, dense sections, trims, thread changes and machine settings change actual cycle time.
Caps can have separate limits
Brother publishes a lower cap-frame speed range than the standard frame range on the PR1055X sell sheet.
The best input is measured elapsed time
For planning, “minutes per 1,000 stitches on our typical job” is easier to audit than a guessed efficiency percentage.
Stress-test purchases
Run the capacity model at a slower measured rate before deciding the upgrade is necessary or sufficient.
Use your own measured data. These guides explain the decision structure. Run the calculators with your actual stitch times, handling times and batch sizes before treating a machine class as a fit.