The implication of "I visit them often enough" with "in a sufficient amount" is also implied by 經常 and 常常. There are times that you cannot translate every single word to convey the full intent. This is cultural biase. In this example, "enough" need not be translated. If you do, then the target translation sounds unnatural and even weird. However, if you want to emphaise "enough" in the translation, then more is needed. For example, I visit them often 我 經常 探訪 他们 enough, 已經够了. Without context, this sort of emphasis in translation can be construed as having a grudge.