Check out this link:
http://www.englishtenseswithcartoons.com/page/adverbs_of_frequency_position
From a communicative standpoint, if you use either order, many native speakers probably wouldn't notice the switch, and the meaning would be the same unless you used inflection to emphasize the auxiliary or the adverb.
However, from a grammatical perspective, in situations such as writing, it's best to stick to the rules in the link above.