How long have the Tucks lived in their home?
It is not possible to give a definitive answer to the question. The text does not indicate specifically how long the Tuck family lived in their home.
The reader does know that eighty-seven years earlier the Tuck family drank from the spring in Treegap. That is when they became immortal. Treegap was not their final stop, so they moved on through the woods until they came to a nearby valley.
They had come out of the forest at last, many miles to the west, had found a thinly populated valley, had started their farm. "We put up a house for Ma and Pa," said Miles, "and a little shack for Jesse and me.
The text says that the Tuck family stayed there for 20 years. Then they were forced to wander like gypsies to avoid suspicion. The family split up and gets together at their house during the first week of August every ten years.
But they come home whenever the spirit moves, and every ten years, first week of August, they meet at the spring and come home together so's we can be a family again for a little while.
I suppose that you could estimate how many times the Tuck family has been back to the house during their 87 years of life, but that would be pointless, because they haven't gone back to that first house. Mae tells Winnie in chapter 10 that they never live in a house more than 20 years at a time now.
But they can't stay on in any one place for long, you know. None of us can. People get to wondering." She sighed. "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."
The best answer that I can possibly give to your question is that the Tuck family has owned their current home for "going on twenty years."