The phrase "have frequently done" is correct and usable in written English.
It is a present perfect verb phrase and it indicates an action that has been repeated regularly in the past but may still continue in the present. Example: I have frequently done volunteer work at the local shelter. In this sentence, the speaker is indicating that they have regularly volunteered at the shelter in the past, and they may still continue to do so in the present. Another example: She has frequently done research on the topic. In this sentence, the speaker is stating that the person has regularly conducted research on the topic in the past, and they may still continue to do so in the present.
Even if you sing harshly sometimes, as I have frequently done, it is a necessity of expression".
Instead, he vowed, as European officials have frequently done in the past, to set out a road map for future solutions.
But, as they have frequently done in their campaigns, both were turning their calendars ahead to the Nov. 5 general election, and saving their strongest barbs for Mr. Pataki.
This may happen especially when some sentences are deliberately removed from the wider context — we know creationists have frequently done that in the past (e.g., Matzke 2010).
Mr. McCarthy, especially in the western phase of his career, has frequently done the same.
But Congress also has the power to impose a settlement, something it has frequently done in the rail industry.
As she has frequently done, Ms. Henley mines the weaknesses of these women, both inherited and self-made, for the humor that will prove their humanity.
It was a matter of some import, then, when a year or so ago, Mubarak began grooming his 37-year-old son, Gamal, an investment banker who had lived in London and who had frequently done business in the United States.
Kundera is a man of the Enlightenment, and is not loath to champion reason over emotion, pointing out, as he has frequently done in his essays as well as his fiction, that many of the worst disasters mankind has suffered were spawned by those who attended most passionately to the dictates of the heart.
Richard Dicker, counsel for Human Rights Watch, said that legal experts who support the court are puzzled at the strength of the opposition to the court, since it gives countries whose citizens are charged with international crimes the right to try them in their own courts, as the United States has frequently done through courts martial when American soldiers are involved in criminal activity.
Although the wildlife agency cannot block lease sales, it can ask for changes in the assessment if it believes it is inadequate, or it can insist on conducting its own survey of potential threats, something the agency has frequently done in the past.
