Full Answer

Google Ads enforces a rolling 37-month retention window on conversion data. Any conversion recorded more than 37 months ago is purged from the account — not archived, not downgraded, but deleted. This affects reporting (you cannot pull year-over-year comparisons beyond the window), audience building (customer lists derived from old conversions shrink), and algorithmic training (Smart Bidding loses the historical patterns that inform long-cycle optimisation).

The impact is particularly acute for WooCommerce stores with high-value or long-cycle products. A store selling premium goods where the repurchase cycle is 18–24 months needs at least four years of conversion data to model customer lifetime value accurately. With a 37-month ceiling, the earliest cohort data falls off before the second purchase cycle completes.

The mitigation is straightforward but requires infrastructure: export conversion data to a system you control before the retention window expires. BigQuery is the natural destination for stores already running server-side event pipelines, because the same pipeline that sends conversion events to Google Ads can simultaneously write them to a BigQuery table where retention is unlimited and under the store's control.

Stores that act before June 2026 preserve their full history. Stores that wait inherit the gap. The data does not come back once it passes the 37-month boundary — Google's deletion is permanent and not recoverable through support requests or API calls. This makes independent data warehousing not a nice-to-have but a structural requirement for any store that uses historical conversion data for business decisions.