How long balls last in a simulator

No source gives a number of shots a ball lasts indoors. What the sources do give is a list of faults that mean a ball should stop going on the mat.

What the makers say to avoid

Elite Screens is firm. Its guide says scuffed, damaged or chipped balls should never be used, and new balls are the aim whenever possible.¹ GolfBays recommends only clean, brand-new golf balls, and warns that worn or marked ones can do more harm.²

There's a cost too. Elite says that if a screen is hit by a damaged golf ball, it isn't considered normal use and the warranty no longer covers it.¹

So the line isn't "when it stops flying well". It's earlier than that. It's when the surface shows damage.

What wear looks like

Wikipedia uses the phrase obvious surface deformation, abrasion or other degradation to describe used balls it calls "shags", which it says remain useful for practice drills.³ That is not a rule for retiring a ball. The retire-it advice comes from the screen makers. Elite Screens says never to use golf balls with scuffs, damaged or chipped ones.¹ GolfBays recommends only clean, brand-new golf balls, as worn or marked balls can cause more damage.²

Here is a simple look-over at the mat:

• Run a thumbnail over the cover. A catch or a rough patch is a flaw.
• Look for a cut, a chip or a flattened spot.
• Check for grey or dark smears. Wipe first, since a clean ball is what the makers ask for.
• Hold it up to a light and turn it slowly.

Cover softness changes the pace

Soft covers wear faster. The reference notes that high-spin cover materials are typically softer and less durable, which shortens the useful life of the ball.³ Practice balls typically have a firmer, more durable cover.³

So a soft-covered ball may need checking more often. How much more isn't something the sources say, so look rather than count shots.

Marks you want and marks you don't

A mark that a monitor needs is different from damage. SkyTrak wants the ball white and clean, carrying a logo or line.⁴ A line that has worn away or smeared no longer does that job.

Screen makers add a separate warning. GolfBays asks for balls free from scuffs, markings or designs.² If your screen's guide says that, a ball with printed marks may be a problem even when it's in perfect shape. Ask the maker.

A simple routine

Keep a small tub for balls you've pulled out. Don't mix them back in with the good ones. Clean a ball that's only dirty, then look again.

Do the check the same way each time. Pick up the ball, turn it, look at the cover and any mark. It takes a few seconds, and it's the habit that the makers' advice really adds up to. Their wording is about avoiding scuffs, chips and marks, so the habit is to look for exactly those.

When in doubt, take it out. A screen's warranty may not cover damage from a damaged ball.

Hit them, check them, and keep people out of the hitting area while you do. The screen's side of the story is in the notes on screen wear.