If a person is always travelling, can he avail himself of the concessions of travel?

Firstly: 

With regard to the traveller who
is constantly travelling, such as sailors on board ships, train drivers,
taxi drivers and pilots, they may avail themselves of the concessions for
travelling whilst they are actually travelling, but when they reach the
place where they live, they must offer their prayers in full, because the
description of traveller has ceased to apply to them. They must also –
according to the view of the majority – offer their prayers in full when
they halt in some city and intend to stay there for four days or more. 

Shaykh al-Islam Ibn Taymiyah
(may Allah have mercy on him) said: 

He should break the fast (and
shorten the prayer) – this refers to the one who usually travels, if he has
a home that he returns to, such as a merchant who brings food and other
items, and such as the muleteer who takes his mounts to bring merchandise
(for a trader), and so on, and like the official courier who travels in the
interests of the Muslims, and others like them. The same applies to the
sailor who has a place on land where he lives. As for the one who has his
wife with him on board the ship and has everything he needs with him and is
always travelling, he should not shorten his prayers or break the fast.

End quote from Majmoo‘ al-Fataawa
(25/213) 

Shaykh ‘Abd al-‘Azeez ibn Baaz
(may Allah have mercy on him) was asked: What about the man who is always
travelling, such as if he is a driver who goes between cities? Is it better
for him to shorten the prayers or offer them in full? And, by the same
token, the other concessions that are allowed when travelling? 

He (may Allah have mercy on him)
replied:

With regard to the traveller who
is always travelling, such as a taxi driver or camel driver, if he is
travelling by camel, as in the past, he may shorten his prayers for the
duration of the trip, and he may put his prayers together for the duration
of the trip. But when he reaches his city he should not shorten his prayers
or put them together, and when he reaches a city where he intends to stay
for more than four days, he should not shorten his prayers or put them
together. But so long as he is travelling, or comes under the rulings on
travelling, or the nature of his work involves travelling, or he is always
travelling, then he is may avail himself of the concessions of travels,
based on the texts of the Qur’an and Sunnah, as both of them classify him as
a traveller. If a person is always travelling, because he is a camel driver
or a taxi driver, he may shorten his prayers whilst he is travelling, and
for the duration of his stay in a city he is passing through, if his stay
will be four days or less.

End quote from Fataawa Noor
‘ala ad-Darb. 

http://www.alifta.net/Fatawa/FatawaChapters.aspx?View=Page&PageID=3375&PageNo=1&BookID=5 

Shaykh Ibn ‘Uthaymeen (may Allah
have mercy on him) said:

Shortening the prayer is
connected to travel; so long as a person is travelling, it is prescribed for
him to shorten his prayers, whether he travels rarely or all the time, if he
has a hometown to which he returns and knows that it is his hometown. Based
on that, it is permissible for a truck driver to avail himself of the
concessions of travel with regard to shortening the prayer, wiping over the
khuffayn for three days and nights, breaking the fast in Ramadan, and other
concessions of travel. 

End quote from Majmoo‘
Fataawa Ibn ‘Uthaymeen (15/264) 

Based on that, you may avail
yourselves of the concessions of travel in two cases:

When you are travelling to the
two countries mentioned in your question

and when you are staying in that
place for less than four days, according to the view of the majority. 

For more information, please see
the answers to questions no. 105844 and
98574 

Secondly: 

With regard to shortening your
prayer in the port, that depends: 

1.

If the person who is working for
the company is resident in another city, other than the city where the port
is, then he also comes under the ruling on travellers, and it makes no
difference in his case whether the port is in his country or in another
country; what matters is his place of residence. 

2.

If he is a resident in the same
city, and the port is within the boundaries of the built-up area of the
city, then when he reaches the port, he is no longer under the ruling on
travel, so it is not permissible for him to avail himself of the concessions
of travel. So he cannot shorten his prayers or put them together, or break
the fast of Ramadan. 

If he is setting out on his
journey, it is not permissible for him to avail himself of any of those
concessions so long as he is still in the port. Rather he may begin to avail
himself of those concessions when he has left the built-up area of the city
in which he resides. 

3.

If he lives in the same city
where the port is, but the port is outside the built-up area of the city,
and is not attached to the residential areas, then in his case the rulings
on travel do not cease to be in effect just because he reached the port;
rather he may continue to avail himself of the concessions of travel until
he reaches the edge of the built-up areas of the city. 

But if he is setting out on his
journey, then he may begin to avail himself of the concessions of travel
when he passes beyond the built-up area of his city, even if he is in the
port or someplace before that. 

Shaykh Ibn ‘Uthaymeen (may Allah
have mercy on him) was asked: If a person is in al-Qaseem and goes out to
the airport, can he shorten his prayers in the airport? 

He replied:

Yes he can shorten his prayers,
because he has passed beyond the built-up area of his town. All the towns
that are around the airport are separate from it. But if he is one of those
who live in the area near the airport, then he cannot shorten his prayers in
the airport, because he has not yet left the built-up areas of his town. 

End quote from ash-Sharh al-Mumti‘
(4/364) 

And Allah knows best.