I don't doubt their drive to repeat, but I do doubt the feat of replicating the mental state they reached last season; fighting figuratively for their lives after being anorexic for seven years.
You mean just like the lieu commun placement I'm talking about in the OP?
The fact a team without a superstar hasn't repeated is only one string of the bow - where the arrow lands won't be because this conventional wisdom you speak of is a cause as to why they'll fail - it's just to add to the fact that the same probability of luck isn't likely to strike two seasons in a row. This is only scratching the surface as to what they'll need to go their way this season:
Secure #1 seed
Largely remain injury-free
All three of Parker, Duncan and Ginobili to maintain their games (relative to what their bodies can cope with)
Role players step up another level and at the right times
Kawhi to develop his game and grow into a star
Maintain the gap on the competition or at least keep them out of team difference
Injuries (e.g. Ibaka last season) to other other squads
Have 50/50 calls go their way in every series and at certain turning/momentum points in games
Ability to stay fresh enough to counter balance the youth of other teams throughout the playoffs
The reliance on other teams' stars not having career performances
The reliance on other teams' role players not outplaying theirs
I could go on and on but you get the point - if any one of these fails to reoccur, it'll break the foundation and cracks will emerge, and when cracks emerge, their % of repeating drops according to the relevancy of each one to where a team can take an advantage of power.
How good this Spurs team is has no bearing whatsoever on any past team that's tried to repeat. Same goes for coaching and same goes for championship winning experience. None of those variables come close to connecting, let alone overlap to suggest that this team might have more of a chance. There's no plausible way you can even measure where they stand against teams that have been in the similar situation, and vice versa.
There's no existing evidence, because the season hasn't resulted yet. What else do we have go on besides judging by a forecast? I see that you and many others are interpreting the evidence differently to what I am, which I personally don't see as being ambiguous, just failure to see when a team's time has expired. And let's be honest a lot of dudes don't even bother to watch other teams besides their own, so we can't work on this idea that they all reached this position through the same reasoning.
I mean it didn't take long for dudes in this thread to spout empty tautologies about the Spurs now did it?
We're are seeing right now why this resting system isn't carrying over to this season. The Spurs are weaker and teams are stronger. They won't be able to take the same approach they did last season and expect to get the #1 seed, another advantage they won't have in the postseason. The size of the snowball they were able to create in the playoffs last season won't be as large this time around.
Like I said the role players played more minutes, and played more of a role in the Championship run last season. It only makes sense that they'll need to step it up another level this postseason, given the above curve. Plus they encountered better teams (Mavs, T'Blazers and Thunder) playing 17 games in 13/14, than they did in 12/13 (Lakers, Warriors, Grizzlies) playing 14 games.
You're basing that off last season, it's not going to be the same again, their responsibility and load will be larger again n the playoffs. Not only because history indicates that, and not only because of the the core's age but just about every team in the playoff picture is considerably stronger this season. We can already see that their dependence on role players through this rest system, won't land them the #1 seed again.