I do it before traveling overseas, on the two cards I use outside the U.S.
I don't bother with alerting the company on the card I use for domestic travel, my pattern of buying gas and groceries out of town is pretty well established,
OTOH, my nephew had a card on his mom's account for use at school, all charges in one city. First time he went into a convenience store in another state, CC company was calling here to report the activity.
A friend on a cruise had alerted Amex of her travel spending plans, but they still kicked on an attempt to charge $10,000 worth of carpets in Turkey, because that was atypical for her. But message came to her phone immediately, she called and settled the issue.
So the card companies track purchasing habits and locations. If you don't usually travel, travel is thus unusual activity.
They will often pick up on "swipe at the pump" activity in an atypical location, or a small charge at a convenience store, because these are the two kinds of purchases most often used by card thieves to check the usability of the account before going for the big purchase.
