"fairly permanent" is a correct phrase and can be used in written English.
You can use it to describe something that is not completely permanent, but that will likely stay in its current state for a long period of time. For example, "The changes that the company made were fairly permanent, with very little chance of being reverted back."
What's more, the changes tend to be fairly permanent.
The Seri have coalesced into two fairly permanent settlements, though they still move about to fish, hunt sea turtles, or sell their crafts.
The chemically inert pigment is fairly permanent and is used as a drawing ink and as an artist's watercolour, particularly in monochrome.
Although an individual's orientation as a motivation seeker or a maintenance seeker is fairly permanent, it can be influenced by the characteristics of his various roles.
"The results from microliposuction are fairly permanent," said Dr. Robert Anolik, a Manhattan dermatologist and clinical assistant professor at Weill-Cornell Medical College.
In 1837 a fairly permanent constitutional monarchy was established in Spain; however, Spanish lawmakers argued that the colonies were not true Spanish provinces and therefore should be governed by special laws.
Likewise, the students' inquiries are abstract and fairly predictable: anencephaly, permanent unconsciousness, eugenic abortion.
It is therefore most helpful to read Milton Osborne's personal and interesting cultural and literary history of this fairly new capital (permanent since 1866).
"Our legislation would simply update our nation's immigration laws to treat binational, same-sex permanent partners fairly," she said on Tuesday.
In Berlin's thinking, they would then be spread fairly and on a permanent basis across the EU, a notion that is extremely divisive and contentious.
She was screaming in such a way that I am fairly certain there is permanent damage to my inner ear.
