A longer cycle may keep heating already-dry areas while a bundled, overloaded or unsuitable part of the load remains damp. The arrangement and programme must be appropriate first.
Understanding this situation
Check whether the problem involves one thick seam, a large tangled cover or the whole load. Those patterns lead to different practical decisions and cannot be reduced to a single extra number of minutes.
A useful next step
Use a garment-compatible finishing method and sort future loads within the manual. Report a persistent loss of performance on sensible loads. Do not apply increasingly long heat to disguise a drainage, airflow or other unresolved appliance issue.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.