How long after treatment should a home be pest-free in winter?

The premise of the question assumes a treatment creates a sealed bubble around a house for some fixed number of days or weeks. It doesn't, because the pests capable of re-entering aren't eliminated from the surrounding area by a single indoor treatment — they're eliminated (or reduced) only inside the structure at that moment. University of Nebraska-Lincoln Extension research on house mice finds they "seldom venture beyond 50 feet from their shelter and food supply," which means any home within that range of a viable food source and shelter sits inside a population that continues to exist and continues to probe for entry, whether or not a treatment happened last week. Rats range further still — Mississippi State Extension documents roughly 100-foot home ranges for Norway rats around structures.

So the honest answer to "how long will it stay pest-free" is: as long as the entry points stay sealed, and not meaningfully longer than that regardless of how recently pesticide was applied.

Exclusion — physically sealing gaps, particularly around foundations, utility penetrations, and roof lines — is what university IPM programs describe as the most successful and permanent form of rodent control, because it removes the mechanism of entry rather than temporarily reducing the population already inside. Missouri Extension's guidance on rat control specifically names "too small a control area, permitting rats to move in from untreated areas" as a documented cause of control failure — the treatment radius was too small, not too weak.

This reframes the useful question entirely. It isn't "how long does the spray last" — it's "how many of the entry points did you find and seal." A company that answers with a specific list of sealed gaps is answering the question that actually determines your outcome; a company that answers with a number of weeks is answering a question that doesn't have an honest number.

Expect some lag and occasional recurrence to be normal, not a sign of failure. A newly sealed home can still see activity for a short period afterward as any rodents already inside are trapped or work their way out, and a genuinely thorough exclusion job occasionally misses a gap that shows up later. The reasonable standard isn't zero activity forever — it's a company that responds to renewed activity by identifying and sealing whatever was missed, not by simply re-spraying and restarting the clock on the same unanswered question.