Praise be to Allaah.
The distance of travel which allows one to shorten prayers is considered to be the distance covered by two days and two nights travel, which is 48 Haashimi miles. This is the opinion of al-Shaafa’i, Maalik and Ahmad(Bidaayah al-Mujtahid, 1/162; al-Majmoo’, 4/213; al-Mughni, 2/255). Their evidence for this was the hadeeth narrated by Ibn ‘Abbaas, according to which the Prophet (peace and blessings of Allaah be upon him) said: “O people of Makkah, do not shorten your prayers for a distance less than four birad from Makkah to ‘Asfaan.” (Reported by al-Daaraqutni,3/139). Some of the scholars have calculated this in current measurements as being equivalent to approximately eighty kilometers.
The length of time one is travelling
The Shaafa’is and Maalikis said: if he intends to stay for four days, he should do the prayers in full, because Allaah allowed us to shorten the prayers provided that one is moving and travelling.
They used as evidence the report narrated by al-‘Ala’ ibn al-Hadrami that the Prophet (peace and blessings of Allaah be upon him) said: “The non-resident should stay in Makkah for three days after completing the rites of Hajj.”(Reported by Ibn Maajah, 1/341).
The Hanbalis said that if he intends to stay more than four days he should do the prayers in full. They used as evidence the hadeeth of Jaabir (may Allaah be pleased with him) who said that the Prophet (peace and blessings of Allaah be upon him) came to Makkah on the morning of the fourth of Dhoo’l-Hijjah, and stayed there on the fourth, fifth and sixth, and prayed Subh (Fajr) on the eighth day. then he went out to Mina, and he used to shorten his prayers.
It is better for you to do your prayers in full when you are at work, because you will be staying there for more than twenty fard prayers, meaning more than four days, and most of the four Imaams said that the person who wants to stay in a place for this length of time should do the prayers in full. To be on the safe side and to avoid being subject to any blame, it is better to do the prayers in full. With regard to the time when you are actually travelling, by land or sea or air, for the distance mentioned in the question, then you know that the Sunnah is to shorten your prayers. And Allaah knows best.