There's no single answer, but there's a clear framework. The right deep-clean frequency depends on three things: how many people live in the property, whether it's a short-let or long-let, and how well the day-to-day cleaning is being kept up.
For long-let domestic properties with a family of four, a full deep clean every 3-4 months is a good baseline. That's kitchen degrease, oven, extractor, inside windows, skirting boards, and behind appliances — the things a weekly clean skips.
For short-let Airbnbs, we recommend a deeper reset every 4-6 weeks on top of turnovers. Turnover cleans are fast and guest-facing; the deep clean is what stops the property looking 'tired' after 12 months of use.
For end-of-tenancy handovers, a deep clean isn't optional — it's the standard the agent will measure you against. Book it as close to the check-out date as possible.
The cheapest thing you can do is keep on top of the small stuff — a 20-minute weekly wipe of the bathroom and kitchen halves the cost of any deep clean you'll book later.