Increases range for spike pile drops, plus piles last longer.
~ BTD6 descirption
Long Reach is the first upgrade of Path 3 for the Spike Factory in BTD6. It increases the Spike Factory's range to cover an increased area from itself, spreading further along the track and potentially to other segments that were previously out of reach without assistance of the range enhancements, such as that from a Monkey Village. Additionally, since Version 21.0, it increases projectile lifespan of all its spikes from 50 seconds to 100 seconds, or +50% for Spike Storm ability spikes (30 seconds instead of 20 seconds).
While it is a cheap upgrade, it is useful in only a few niche situations, spreading the damage out for a tower mostly centralized on single area blockage while only improving lifespan of its spikes as a bonus. The purchase of this path also has a disadvantage in the short-term of picking between Bigger Stacks and Faster Production. The Long Reach upgrade pairs well with Path 2 upgrades overall, as the benefits become more prominent with its succeeding Path 3 upgrade, Smart Spikes.
This upgrade is useful on Apopalypse Mode, but alternate options will generally suffice much better.
There is little meaning to stop at just Long Reach without getting its further upgrade Smart Spikes. Try upgrading to Smart Spikes as soon as possible.
Because the base Spike Factory projectile lifespan is dropped from 70s to 50s in Version 22.0, it might be worth purchasing Long Reach for the increased spike lifespan per round, but buying this upgrade sacrifices either the faster spike regeneration rate from Path 2 or the larger spikes from Path 1.
0-0-1 Long Reach is a lot cheaper than adding a second Spike Factory, and can actually be valued much more the more round stalling is applied.
The benefits Long Reach can be a useful addition for Spike Storms, thanks to allowing the ability spikes last considerably longer, though generally it's better to also add Smart Spikes too, so that the Spike Storms can further benefit.
Since Long Reach arguably had almost no purpose outside of certain maps where the bonus range was necessary, and was even considered negative for the Spike Factory, Long Reach now additionally adds bonus projectile lifespan. This has made crosspathing with Path 3 a little more worthwhile, but not by a long shot.
Long Reach now increases projectile lifespan (70s --> 100s)
Long Reach now makes Spike Storm ability spikes last 50% longer.
Description changed to reflect the buff.
Changed from "Increases range over which spikes can be deposited." to "Increases range for spike pile drops, plus piles last longer."
This change was not directly documented in the Patch Notes, however the balance change was.