Actually...I remember that a CD can have a max of 99 tracks and not more than that... Similarly a DVD can have a maximum session depending on the media and format (+R or -R)... DVD+R can support 154 while DVD-R supports 169. Although it very much depends on the drive fro reading and writing... Most of the time anything above hundred can cause problems reading..... But then 10-20 sessions is pretty normal on both +R and -R..... I have done a maximum of 25 sessions...
One more thing the +R camp mentions, that data retrieving from sessions is better in their format. But who knows if the alliance is correct or not...
As much as I remember those werent readable in Win 98, but all of those worked fine in WinXP...