When they are placed in initial position, yes. Fronting of adverbials (not just adverbs of frequency) gives them prominence and is always done for a reason. But not in end position. For adverbials with two words or more (frequency adverbials of this type include on Fridays, twice a week
), end position is the "default" position : I go to the gym on Fridays.
Moving an adverbial to initial position, however, is always done for a reason, and if there's no reason it sounds strange. Consider the adverbial every day
in the next example :
A : Do you sleep late in the morning?
B : No way! I get up at 5.30 every day!
It would sound strange as No way! Every day I get up at 5.30!
But now consider the alternative response ... B : On work days I get up at 5.30, but at weekends I sleep till 8 or 9.
Here the adverbials on work days
and at weekends
are brought to the front of the clause, because of the contrast. Here's a possibly clearer example with two time adverbials by 5.30/by 6.30
: I'm always up by 5.30, and by 6.30 I've showered, had breakfast and am on my way to work.
In the first clause by 5.30
is in the default, final position. But by 6.30
is fronted to the beginning of the second clause. If it hadn't been, the sentence would be .. I'm always up by 5.30, and I've showered, had breakfast and am on my way to work....
leading the listener to think that all of these things had happened by 5.30, and therefore meaning that s/he has to revise the expection when s/he hears the final words .. I'm always up by 5.30, and I've showered, had breakfast and am on my way to work by 6.30.
Quite possible, but it opens the door to misunderstanding. By fronting the adverbial, the change of timeframe becomes clear from the start and there is no risk of ambiguity.
There various reasons for fronting adverbials. This thread
looked at the effect of given-new organisation in English which, incidentally, is also an explanation for the I get up at 5.30
In the specific case of the one word adverbials of frequency then, I'd suggest that it's the same as the others : end position is a default option, while initial position is a "marked" option - it's done for a purpose. With the one word adverbs, though there's also the choice of mid position - so they have two "default" options. Is there a difference?
I'd hypothesise that end position is probably more usual in spoken language than written, as it's often used to tag the adverb on the end as a sort of afterthought or simplification. We've seen that deciding where to place the adverbial in the verb phrase is quite complicated. I'd therefore hypothsesis that when speaking in "real time" it's easier for the brain not to worry about the rules, but just tag it on the end. I go to the gym on Fridays, usually.
In writing, on the other hand, there's plenty of planning time and more likelihood therefore of mid position.
Unfortunately the concordancer I usually use is off-line at the moment, so I can't check this, but I'll try again later and add a second reply if anything comes out of it.