Perma-Spike



Perma-Spike is the final upgrade of Path 3 for the Spike Factory in BTD6. It allows spikes to last utterly indefinitely. This allows spikes to be stockpiled indefinitely as rounds go by, thereby making the upgrade much more valuable in the long-run. These spikes absolutely will never disappear until touched by a bloon. It costs $TBA on Easy, $22,000 (?) on Medium, $TBA on Hard, and $TBA on Impoppable.

Tips

 * Always purchase this upgrade on single-entry-single-exit maps near the end of the track. Then spikes won't be used up immediately, allowing spike stockpiling to slowly make the tower more and more valuable.
 * Likewise, never sell a Perma-Spike unless you've messed up its positioning. Even so, that should've been planned much earlier.
 * Always purchase the Path 2 upgrades (Faster Production and Even Faster Production), as they will produce spikes faster than a Bigger Spikes pile alone would produce. This is unless you want it to be emergency DDT-popping power, which is probably the better option if DDTs is a major weakness of your defense.