They will be sending a new build of the flight software at the end of the month. This will improve the hazard avoidance software and offer a 'deep sleep' mode which allows the rover to totally shut down as a power saving exercise overnight.

They regularly drive without the hazard avoidance software running as it is - this is called a 'blind drive' and is usually the first 10 - 15 metres of a days drive, after which they might command an autonomously navigated drive of a similar ammount. This is because they can only see the first 10 - 15 metres at enough of an angle to gauge the driveability of it.

I cant imagine that Spirit will be doing any drives longer than 10 - 15, maybe 20 - 25 metres of blind driving on it's way to the Columbia Hills to the south - the terrain is just too rugged ( although it might even out a few hundred metres south of the crater )

At Meridiani for Opportunity, the terrain looks 99.9% clear of any obsticles and it would appear they could quite easily command a blind drive of 50 metres, 100 metres, or maybe even more -as there is no need for the hazard avoidance process to occur ( which breaks the drives down into 30 cm steps, after each of which it takes stereo imagery of the terrain infront, generates a 3d model, and plots a suitable path thru it, then drives the next 1ft ) - so blind drives are much much faster, and thus one can cover a longer distance in a shorter time, which leaves more time for charging batteries.

Doug