| Share | Phrase |
|---|
| 39.06% | prolonged [time duration] period |
| 14.49% | prolonged [time duration] use |
| 8.82% | prolonged [time duration] exposure |
| 7.70% | prolonged [time duration] time |
| 6.10% | prolonged [time duration] operation |
| 4.64% | prolonged [time duration] waiting |
| 3.46% | prolonged [time duration] part |
| 3.32% | prolonged [time duration] life |
| 2.78% | prolonged [time duration] usage |
| 2.73% | prolonged [time duration] condition |
| 2.42% | prolonged [time duration] contact |
| 2.21% | prolonged [time duration] combustion |
| 2.20% | prolonged [time duration] duration |