I don’t think party fatigue is cast in stone, it has just been part of the dynamics of the past 60 years. If Gore maintains a steady economy, he wins in 2004. If the crisis hits in 2008, he initiates a TARP program but his Republican successor is far less aggressive than Obama and there is barely recovery; more businesses fail. One GOP term and a Democratic sweep in 2012. On the other hand, the Dems will be up against some very lofty expectations that might make two-term presidents unlikely for several election cycles.
That would mean five out of six elections would have gone to the Democrats. Which honestly I just don't see happening without the creation of a New Deal-esque coalition of voters.
Remember even if Gore won in 2000 that election was close against the backdrop of a successful economy. The Republicans are much more in contention than the 1930s yet you actually have them doing worse than when they were the party of the Great Depression!
If a hypothetical Republican elected in 2008 has managed to bring even a slight recovery I don't see voters stampeding for the party that will still be blamed, fairly or unfairly for 2008.