Whilst the guide is correct in general, during my years of doing idocs I have found that the periods for each stage are pretty much similar, each stage going a certain length of time, EXCEPT that there is a random factor within them. On rare occasions ANY period may go an extra hour, doesn't happen often but it can. The final stage I have found to normally be around 6 hours and 55 mins, the period listed may have been correct once but it certainly is not currently. Good luck with future idocs, much better that decent (esp rare) items stay in the game rather than simply fall to the ground and decay.
I forgot to mention that the items listed as disappearing no longer do, these now redeed and can be picked up too.