If you follow the conversations on Doug's site with one of the actual Spirit rover drivers, you can see that attempts to free it are being planned and implemented. I just have a gut feeling that you can only do that so many times and then it becomes the point of diminishing returns. Very little new science is getting done during those stuck times and the data you do get back gets very redundant very quickly.

If Opportunity loses a wheel and goes into drag mode like Spirit the chances of her reaching Endeavor Crater are next to nothing. The amount of non-roving time that ensues every time wheel currents spike tells me that's a real possibility. Oppy is on a vast plain with few unique targets to look at, just lots of dunes with a few redundant rocks scattered about.

Of course there will be years of poring over the data that's already been returned but a large part of that can be done by the supporting universities. It doesn't take up staff at JPL and active data communication links (and valuable dish time).

Often the data must be routed through Mars Orbiters using bandwidth they could possibly utilize better with their own instruments.

Here's a guarantee for you though. The next rover will have a system to put a wheel into free rotation if its drive motor goes out.

Art