There are two problems with stronghold/domain play at higher levels.
The first is that while it makes perfect sense for the characters to want semi-retirement where they can live off their ill-gotten gains in relative comfort, it's a pretty bad reward for the players. "OK, now you've gotten to 10th level and learned to enjoy the game, so now it's time to change to a different style of game."
The second is that domain play, at least as presented in previous editions, leaves something of a bitter aftertaste when combined with modern sensibilities. The base conceit is that you go somewhere on the borderlands of civilization, build a keep that might one day expand into a castle, raise an army, and then proceed to kick out any monsters in the nearby region. Basically, you are now the conquering horde.