We've just deployed an A/B test with a simple 50/50 split.
The test has been running for 3 days and the current split is 66% control, 34% test for 222 visitors (we're using Analytics for Target as the reporting source). Yesterday, it was an 80/20 split between the control and test variants.
The test itself deploys a client side redirect if the customer has a specific cookie value (we're not using the built in redirect to page option in Target as we need to modify the cookie value before applying the redirect). The audience is based on customers hitting the site with a specific query parameter value.
There haven't been any changes since activation (i.e. pausing and reactivated, changes to audience, etc.) so I'm just wondering if there's a ballpark figure where we can expect the numbers to even out as required.