Myth: a 30-second ad refresh timer is the sweet spot

Myth: a 30-second ad refresh timer is the sweet spot

Everyone copies the 30s number. It's a Google viewability default, not an RPM optimum.

What it does — re-requests a unit on a timer to bill more impressions per session.
Setup effort — 2/5 (one config block).
The correction — refresh should fire on active time + viewability, not wall-clock. A 30s timer on a scrolled-past unit burns inventory at junk viewability, tanking your viewable-CTR and your bid floor.
RPM lift seen — event-based (viewable 30s + tab focus) beat blind 30s by 12-18% on long-read pages.
Pros — same fill, cleaner demand.
Cons — needs a real refresh manager (vs the native timer), more QA.

Lift: ★★★★☆ — Risk: ★★☆☆☆
Best for: dwell-heavy content. Skip if sessions are under 20s — you'll never hit the second impression anyway.