Direct answer first: Grunt calls are typically worth using in waves, with timing that depends on the season and deer behavior. A common practical guideline is to use short, energetic grunts every 20–30 minutes during the pre-rut to rut, and to space calls farther apart (roughly every 30–45 minutes) in early season or post-rut. The rut is when bucks respond most reliably to grunts, and during that peak you can escalate to more frequent, louder sequences. Details and practical guidance

• Early season (pre-rut): Grunt every 40–45 minutes or so, with moderate volume. The goal is to imitate a neighboring buck’s presence without overdoing it. If you see signs of one approaching, you can shorten the interval slightly and increase urgency.
• Pre-rut to rut transition: Increase frequency to about every 20–30 minutes, and use more pronounced, attention-grabbing sequences (for example, a short series of 5–10 seconds with 2–3 grunts, followed by a brief pause).
• Peak rut: This is the best time to crank it up. Use loud, directional, 5–10 second sequences every 15–20 minutes. The sound should imply an intruder or a rival buck; many hunters report buck attention and approach during these periods.
• Post-rut: Slow back down to longer intervals (around 30–45 minutes) and softer grunts, since bucks are less responsive after the primary breeding period.
• Variation matters: Avoid monotone calls. Change volume, cadence, and intensity to mimic a real buck’s behavior and to keep deer guessing.
• Setup considerations: Use grunts from a stand near bedding or between feeding and bedding areas. Your calls should sound like a real deer interacting with a rival or with a doe, not a rehearsed pattern.
• Don’t overdo it: If no deer responds after a few cycles, consider changing spots, adjusting wind, or trying another lure or calling approach (bleats, rattling) rather than hammering the same call.

If helpful, I can tailor these guidelines to your specific region, season, and hunting method (bow vs rifle) and give a proposed calling schedule for a 2–3 hour hunt based on typical deer activity in that area.