Some foreign speakers produce sentences like Je reste en France pour six mois (≈ "I am staying in France for six months"), combining the preposition pour (≈ "for") and the verb rester (≈ "to stay") to express "duration". However, if the English version seems to be tolerable, the French one is not acknowledged unanimously by French native speakers. A part of them considers such as a construction acceptable and the other part is uncertain and prefers the use of pendant (≈ "during") to pour, but without any conviction. Such a report is intriguing and deserves a meticulous study. We believe that the observed hesitations are due to two sorts of linguistic phenomena: firstly, the "signified" of the French preposition pour is not compatible with the aspectual informations implied by the use of rester since pour involves, in uses including the structure "pour Nduration", that the final boundaries of the duration are fuzzy and unclear; thus, pour is incompatible with numeral quantifiers like deux, trois, cinq, etc. (mois) ("two, three, five (months)"), while the verb rester calls to mind an "unlimited interval". Secondly, speakers may confuse pour with pendant which expresses more clear boundaries in sentences like Je reste en France pendant six mois. In addition, the aspectual properties of rester can also be wrongly considered as the same as the other "static verb" être ("to be"): the latter accepts, for example, the combination with inchoative process but not the former. That's why native speakers are not convinced about the heard patterns. Our hypotheses are confirmed and supported, in this study, by a large corpus of sentences and several linguistic criteria.