Is it permissible for a traveler to combine prayers sometimes and not combine them at other times?

The permissibility of combining two prayers for a traveler is a Prophetic Sunnah (definition), and the Prophet, peace and blessings be upon him, did it in Medina so as not to inconvenience the Ummah. The proof for the permissibility of combining prayers is his saying to Ibn Abbas: "(The Messenger of Allah, peace and blessings be upon him, combined the Dhuhr and Asr prayers, and the Maghrib and Isha prayers in Medina, without fear or rain. [In another narration: and without travel].) It was said to Ibn Abbas: Why did he do that? He said: So as not to inconvenience his Ummah." Some scholars were of the opinion that it is not permissible for a traveler to combine prayers if he is settled, but the correct view is the permissibility of combining prayers for a traveler, whether he is on the move or settled. Ibn Uthaymeen was of the opinion that it is better for a settled traveler not to combine prayers, but if he does, there is no harm, unless there is a need to combine, in which case combining would be better. Ibn Baz was of the opinion that a resident traveler has the choice between combining prayers or not, and it is better to pray each prayer at its appointed time, unless there is a need to combine, in which case there is no harm, with the reminder of the obligation of congregational prayer for the traveler, so it is not permissible for him to combine and pray alone.