Test duration planning

Test duration determines how long an A/B test should run to provide reliable results. Running tests for too short a time risks making decisions on incomplete data, while running too long wastes opportunities to implement winning changes. The right duration balances statistical significance with business cycles.

A good test duration covers at least one full business cycle, typically 1-2 weeks minimum. For example, an e-commerce site sees different shopping patterns between weekdays and weekends — stopping a test after just 3 weekdays would miss weekend behavior. Similarly, a B2B product should test through both peak and quiet business hours to capture all user patterns.

Seasonal events also significantly impact test timing. Running a pricing test during Black Friday or comparing homepage designs during a major product launch will give skewed results. Wait for "normal" business periods unless you're specifically testing seasonal features. Similarly, marketing campaigns, competitor launches, or market events can all create temporary behavior changes that affect test validity.