Spindle hours are the machine-tool equivalent of miles on a car — the clearest single indicator of use and remaining life. There's no hard cutoff: a well-maintained machine can run well past 20,000–30,000 hours, while a hard-used, poorly kept machine can be tired much sooner. Context matters more than the raw number.
Weigh hours against age (low hours on an old machine can mean it sat, which brings its own issues), the type of work it did, and the condition of the spindle, ways and ballscrews. Hours are one input among several — value the whole machine, free, at The Machine Blue Book.
Get a real number from a Machine Blue Book specialist — free, no obligation.
