If the time for the option is not fixed, will the deal be considered as legal?

Narrated Ibn 'Umar:

Allah's Apostle ﷺ said, "The seller and the buyer have the option of cancelling or confirming the deal unless they separate, or one of them says to the other, 'Choose (i.e. decide to cancel or confirm the bargain now)." Perhaps he said, 'Or if it is an optional sale.' " Ibn Umar, Shuraih, Ash-Shabi, Tawus, Ata, and Ibn Abu Mulaika agree upon this judgment.

حَدَّثَنَا أَبُو النُّعْمَانِ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، حَدَّثَنَا أَيُّوبُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ قَالَ النَّبِيُّ ﷺ " الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا، أَوْ يَقُولُ أَحَدُهُمَا لِصَاحِبِهِ اخْتَرْ ". وَرُبَّمَا قَالَ أَوْ يَكُونُ بَيْعَ خِيَارٍ.