Now now, knock before crossing the bridge sir. Not silly at all. The point I am making if you read what I said is that some cash in hand and some ability to spend via cards would allow the spending party to convince themselves through daily checking (the rates are on many peoples start up pages on their computers) that they are using the most efficiently exchanged funds. I am in no way suggesting daily exchanges based on the daily rate fluctuations. That would be silly indeed.

As to what credit card one might use to act most efficiently, I would suggest that getting a card which charges fees in the first place is rather inefficient. Personal banking preferences aside, it is not only residents but also casual visitors who can act efficiently. I suspect there are options of that nature for residents of the US and other places as well.

I completely agree that trying to optimize behavior to the extent of it costing you more than your time is worth is important, but I do not believe that means one should not avail themselves of the best cards for their spending patterns. If those patterns involve international travel, it may be wise to bear that in mind when signing up for cards.