Marathon Boss/Playing With

Basic Trope: Boss battles that takes ridiculously long time to beat.

Straight: In the RPG Heroes of Troperia, the Final Battle against Emperor Evulz lasts for about 40 minutes.
Exaggerated: It takes about 10 hours to defeat Emperor Evulz.
Up to Eleven: It takes at least a WEEK to defeat Emperor Evulz.
Justified: Emperor Evulz has recently obtained a power that makes him nearly impervious to most attacks.
Inverted: Rush Boss
Subverted: Wielding the Sword of Plot Advancement can overcome the damage cap in the Final Battle, making the fight way shorter than it normally is.
- It doesn't take you that long to fight him, you just need to take that long to get an achievement.
Double Subverted: ...which means instead of 10 hours battle, you get 40 minutes battle.
Parodied: Emperor Evulz actually urge the player (yeah, you) to take a break every now and then in the Final Battle.
Deconstructed: The heroes may have vanquished Evulz, but the player vanquished their sanity.
Reconstructed: They take a long rest thereafter.
Zig Zagged: Depending on the whim of the Random Number God, Emperor Evulz can have anywhere between ten thousand HP to ten million HP.
Averted: The battle against Emperor Evulz is only slightly longer than average boss battles in any RPG.
Enforced: The developers realized they slacked off on level design and made their game shorter than players expected; in a desperate attempt at last-minute Padding, they made the Final Boss take ridiculously long to beat.
Lampshaded: "Prepare for a long fight!"
Invoked: Emperor Evulz studies defensive tactics above all else, in order to make the inevitable fight with the heroes take as long as possible.
Exploited: He does this so that they give up in frustration and/or go insane after fighting him for an hour.
Defied: Emperor Evulz realizes that while turning himself into a Stone Wall may be practical, it makes for an incredibly boring fight, so he becomes a Glass Cannon instead.
Discussed: "We do have the power to take on Emperor Evulz' generals... but do we have the time?"
Conversed: "You've been fighting this boss for what, an hour?" "Yes! And I cannot even save in mid-fight!"

Take this! And this! And this! Argh why won't this guy die?! *40 minutes later* Okay, you may go back to Marathon Boss.