They said the same thing about the Circus Tour back in 2009 and then Femme Fatale Tour in 2011.
A residency is in NO way, shape, or form any more complicated than a world tour, which had a show every other day vs. ONCE a week with Vegas. Not to mention the constant back and forth travelling with a world tour, that is now nonexistent with a residency. And there's also the fact that she'll have a permanent living facility as opposed to having to stay in hotels or her tour bus for months straight.
Like, how hard is it to understand? If she can do a tour TWICE since her breakdown, she can do one show every other week for 2 years.