Bellarmine's explanation: not for a longer time
Bellarmine says much the same. Explaining in what sense he had denied that all the moral precepts can be kept as to the substance of the work by the strength of nature alone, he writes: 'We do not mean that no one can keep them all for a very short time. It can happen that for a while no affirmative precept arises and no temptation urges us to break the negative ones.
So the sense of the proposition is that over any longer time, in which various precepts present themselves to be kept, they cannot all be fulfilled by the strength of nature alone in such a way that sin is wholly avoided.' De gratia et libero arbitrio, book 5, chapter 5.
Latin
XVIII. Quibus similia apud Bellarminum quoque leguntur. Explicans enim quo sensu negaverat, solis naturae viribus servari posse omnia praecepta moralia secundum substantiam operis, significare non volumus, inquit, non posse aliquem ad brevissimum tempus omnia servare: cum possit fieri, ut aliquando nullum occurrat praeceptum affirmativum, & nulla adsit tentatio provocans ad violanda praecepta negativa. Itaque sententia propositionis illius haec est, ut non possint longiore aliquo tempore, quo varia praecepta observanda se offerunt, solis naturae viribus, ita omnia adimpleri, ut omni ex parte peccatum vitetur. De gratia & libero arbitrio lib. 5. cap. 5.