I run both hump packs and dry cell packs. I use the dry cells as a backup in case I drain the humps at the track or bashing. At any rate, either pack type should last at least a good days worth of running, sometimes longer depending on the track, site and style of driving. Just remember a couple of things about Rx pack life; The following will all make the pack charge shorter 1) if there is binding or alot of resistance in the servo linkage 2) the total servo travel is more than the link will allow, 3) you hear a buzzing from the servos, 4) the more ya turn, and 5) using the throttle and brakes alot. All in all, any pack in just about any r/c truck should last a minimun of a whole day at the track. Also, the torque of the servos affect the pack life, generally the higher the total torque output, the more juice that servo will drain from the pack.
One other note on dry cells, ya get what ya pay for. If you find some dirt cheap, no name battery, they will not last as long as a good battery. I prefer Energizer if I have to use dry cells. Yes, they are more expensive, but I have gotten 2 or 3 days of running from a pack before I had to change them. Changing batteries in a Savage is also a pain, so I try to max the pack before I have to change it.