After a while, habit picks for you

The sequence, which is not dramatic

1. You pick one arbitrarily, for no reason.
2. It works, so you use it again, still for no reason.
3. It becomes the one your browser completes, the one you recognise, the one you would recite if asked.
4. The other two stop being addresses you have and become addresses you know about.
5. At some point the one you use stops answering, and you discover which of those two things you actually had.

Why this is worth a study

Nothing in that sequence involves a mistake. Every step is reasonable. The problem is that it quietly converts a set of three into a set of one plus some background knowledge, and background knowledge is not something you can paste.

The whole benefit described in what a second address buys you is collected only by somebody who can produce the other strings at the moment they need them. Habit does not remove them from your store, but it removes them from your reach, which has the same effect on the day it matters.

Recognition is not possession

The specific danger is recognition. After using one string for a while, you will recognise it on sight, and recognition feels like knowledge. It is much weaker than it feels.

Recognising a string means you can tell it is roughly the shape of the one you use. It does not mean you would notice a substitution in the middle of it, and the studies on characters from two addresses and typing from memory are both about the gap between recognising and holding.

The second effect: the other two go stale in your head

If one of the ones you never use were retired and replaced, you would have no way of noticing. Your habit is doing nothing to keep your copy of the set current, and it is also removing the occasions on which you would have looked.

A reader who uses all three occasionally at least has a chance of noticing when one of them stops behaving. A reader who uses one has no information about the other two at all, which makes the absence section much harder to apply when they need it.

What habit is good for

Habit is not the enemy here. A habit of pasting rather than typing is worth more than any amount of care. A habit of keeping the set somewhere you can reach is the single most useful thing in this site.

The problem is narrow: a habit attached to one member of a set, in a situation where the point of the set is that it has members you can fall back on.

The cheap counterweight

Use a different one occasionally, for no reason. That is the whole intervention, and it is the subject of rotating on purpose. It costs nothing, it keeps all three in reach rather than one, and it means the day you have to use a different address is not the first time you have done it.

How to tell if it has happened to you

Ask yourself which of the three you used last. If you can answer without checking, habit has already picked for you. That is not an emergency and it does not need undoing. It is a reason to make sure the other two are somewhere you can paste from, rather than somewhere you know they exist.

The version of this that catches careful readers

Somebody who has read all of this, stored all three properly, and understands the argument can still end up using one address for months without noticing. Understanding does not prevent habit, and habit does not announce itself.

What prevents it is a physical act performed occasionally rather than a belief held continuously. That is the only reason the rotation study exists as a separate piece of advice, and it is why it is phrased as something to do rather than something to know.

What this study is not. It is not a warning against having a favourite, and nothing goes wrong until the other two stop being things you can produce on demand.