Lingering Magic

 is an upgrade in the Magic Monkey Knowledge tree. It increases the lifespan of all Magic Monkey projectiles except Alchemist by +20%. It has no prerequisites.

Summary
Lingering Magic is pretty straightforward, as it increases the lifespan of most Magic Monkey projectiles by +20%. Homing projectiles such as Ninja's Seeking Shuriken and Wizard's Guided Magic will last longer, which allows these projectiles to seek bloons from further. But most importantly, this MK allows Wall of Fires to last longer too, for almost 100% uptime.

Tips

 * While this MK sounds simplistic in value, since all it does is increase projectile lifespan, this MK has greater merit for very specific upgrades. More specifically, the greatest value that can be taken from this MK is increasing the Wall of Fire's lifespan from 4.5s to 5.4s. Because Wall of Fire's attack rate is every 5.5s, there is now almost 100% uptime for the Wall of Fire attack.

Trivia

 * The observation of "+20% lifespan" for all affected Magic Monkey projectiles is determined by three facts about Wall of Fire: the Wall of Fire attack is affected by this MK, a default spawned Wall of Fire has a lifespan of 4.5s, and a Dragon's Breath without MK will have literally 100% uptime with the Wall of Fire attack. Having observed that a Wall of Fire lasts for almost 100% uptime without attack speed buffs, and 4.5*1.2 is equal to 5.4, a neat number, it is concluded that all other affected Magic Monkey projectiles would also last for +20% longer too.