в течение продолжительного времени

• It is unlikely that anyone would be irradiated by a single beam for any length of time.

• A child who has suffered undernourishment very early and for an appreciable length of time will never reach normal size for his age.

• The text was developed over a protracted period of the last 10 years.

• The screens are designed to give maximum output over prolonged (or extended) periods.