Even peace may be purchased at too high a price.

Quiet is not the same as things being well. There are arrangements that stop the arguing by requiring one person to disappear a little, and from the outside they can look like harmony. The cost gets paid privately, in the things nobody can say any more, and it usually keeps getting paid.

If a relationship has gone smooth, ask what topics have quietly left the room. Raising one of them will be uncomfortable for an evening. Weigh that against another year of the arrangement you have, and choose on purpose rather than by default.