How much time are you prepared to spend in a "players vs bosses" kind of map?

Hello!
I am currently balancing the pacing of my map, and so I would like you to answer here how much time are you prepared to spend playing a "players vs bosses" kind of map

Here is how it works in my map:

The game takes place in the forest troll temple city, Zul'Aman

First the players pick a hero each, there are three types of heroes, Tank, Damage Dealer and Healer, there can only be two tanks, 5-6 damage dealers and 3-2 healers (a total of 10 players)
Their hero spawns at a camp outside Zul'aman, and the players can pick up some quests that hopefully will add flavour and help guide them through Zul'aman.
When everyone are ready the players can start a small (hopefully a little funny) event that opens the gates to the troll city, and then they can begin fighting the trolls and bosses.
There are a total of 6 bosses, and at the beginning you can fight 4 of them. The 4 first bosses can be fought in any order, but there is a recommended order to kill them (difficulty and time reasons). Each boss is guarded by "gauntlets" with groups of normal trolls (2-5 trolls in each group) that must be killed before being able to reach the boss.
Once the four first bosses are dead, the fifth boss is accessible, and when the fifth boss dies the players can reach the sixth boss (who is an mad troll warlord of Warcraft 2 fame).
When the sixth boss is dead, players get a highscore showing how well they performed. The score can be improved by defeating the first four bosses in under 20(subject to change) minutes, there must be no failures at bosses or gauntlets to beat this timer.


Now, my question again:

How much time are you prepared to spend playing a map like this?

Currently the map takes around 30 minutes to beat if you know exactly what to do and no failures, taking the straightest most efficient route to everything. With failures and learning, maybe 1h to 1h30min.




EDIT: The forums logged logged me out when I posted so I couldn't attach a poll to this thread even though I wanted to =(

I think I'd fight through it for 45 minutes at the least. If it felt like I was getting somewhere, I might continue, otherwise I'd quit.

30 minutes should be your limit, more time makes players get tired...

45 minutes. My experience with these types of maps though consist of 5 minutes of play then 2 minutes of players complaining about other players than 5 more minutes spent at the lobby during the remake.

You should never be able to beat the map on the first try with random people who've never played, if you can its way too easy. 45 minutes should be a good give up failure point as well.

I think 40 min is maximum, unless your game is really good.