How long do TemporaryOnRez objects last?

The Wiki says between 60 & 70 seconds and that has been my experience. I'm wondering what other people's experience has been.

I want to create a temporary object that rezzes a copy of itself right before it dies. So I set a timer to 55 seconds for it to do that then it llDies. The point is that I want to be quite certain that the copy will be created so I want to set the timer as late as possible but also be very certain that it will have time to execute the rezzing code before it dies. Does 55 seconds sound ok?

if an avatar is SEATED on the temporary object, it can last indefinitely.. though if it lasts longer than 60-70 seconds, it seems to vanish the very second that the avatar(s) get up.

I'd go with 30.. a "self replacing object might work something like this.

Object A rezzes
30 seconds
Object A rezzez object B, gives copy of Object B to Object B
30 seconds
Object A vanishes
Object B rezzes Object C, and gives copy of object C to object C
30 seconds
Object B vanishes

Of course then you're actually creating 2 of the objects. but you could create a situation whereby the rezzing on Object B makes Object A change to transparent, or something.

It really depends on what you're actually trying to accomplish. 55 seconds might be enough overlap to reduce blinking.. but how best to do this really does depend on what you're rezzing. if it's a shiny thing, you're going to have a heck of a time keeping it from flickering.

Just remember, temp rezzers for "Cheating" the prim limit on your land, aren't very friendly to your neighbors.

temp prims can last for up to about two minutes though there is absolutely no way to tell how long they will actually "live" as sim load factors in to those prims life times and due to human influence, cannot be predicted all too well. High sim load does influence llSleep() and lsl timer events quite badly which may throw off your timer just enough for the rez-in-time-before-deleted script to perform the "epic fail" ceremony.