Position of adverbs of frequency

I think that both are acceptable. At least, both are used.

Personally, I prefer "you often do" to "you do often", but (as I said) the latter form is also used.

Of course, the rule says what Yahyacan explained. In any case, I've googled the expressions "sth. you do often" and "sth. you often do".

For the former, there are 606 results.

For the latter, there are 76 results.

I'm not saying that googling a word or phrasing proves that it is correct, but it certainly tells us a lot about how people use it.

These adverbs of frequency can shift about quite readily (I often/usually don't see; I don't often/usually see; Often/Usually, I don't see; I don't see my children often/usually), but the standard place for a single-word adverb relative to a verb phrase is after the operator (here, don't -- I don't usually go).

Other adverbs are not so flexible, like adverbs of time, which usually come at the end:  I don't see my children Tuesdays.  Tuesdays can only go at one end or the other of this sentence, not in the middle.  Adverbs of manner also do not precede the operator:  I don't willingly go to parties; I don't go to parties willingly.
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