How long had the Tucks lived in this house?

In Chapter Ten, we learn that the Tucks have lived in their house for "going on twenty years."

"We been in this house about as long as we dare, going on twenty years. It's a right nice place. Tuck's got so's he's real attached to it. Then, too, it's off by itself, plenty of fish in the pond, not too far from the towns around. When we need things, we go sometimes to one, sometimes the next, so people don't come to notice us much. And we sell where we can. But I guess we'll be moving on, one of these days. It's just about time."