I just recently finished what I suddenly realized could have been a colossal waste of my time. I decided I wanted a slime farm, so using the slime finder app and this tutorial
I built myself a farm (slightly modified, as I built mine exactly within the two consecutive chunks, instead of expanding four chunks around a center). Here's where I'm wondering if I'm screwed out of this being effective.
I know that mobs can't spawn within a 24 block sphere of myself, but they also have a chance of despawning outside of a 32 block sphere, and despawn completely if they're outside a 128 block radius sphere.
The farthest corner of my spawn area is at coordinates (X: 128, Z: -16, Y: 10), while the collector I built from the end of the tutorial is at (X: 80, Z: -34, Y: 72), which, assuming I did my math right, is a distance of about 80 blocks (straight-line distance, so I don't know how that changes with actual blocks). This means that, just waiting at my collector, any slimes that do spawn have a pretty dang good chance of despawning before they reach the collector.
So, supposing I put my collector right above the ladder that the slimes are supposed to climb, now I figure out what height I need to be in order for them to never have a chance to despawn. If my ladder is at coordinates (X: 112, Z: -32), I find that my collector has to be at a height of (Y: 32) in order to keep any slimes from despawning at all. Obviously I'd want to raise it just a bit, probably about 8-10 blocks to make sure I don't prevent any slime spawns closer to my collector, but that's still a pretty good ways down from where my collector is now. and the whole point of putting the collector at its original location was to have it near my base.
So yeah, I can't help but feel that digging even those two chunks out was a colossal waste of time. Now obviously I can dig out another couple of layers of farms in those chunks to help increase my chances, since I believe slimes spawn up to (Y: 40), but that's a lot of work for a payoff I'm not sure I'll get.
I guess I'm either looking for someone to find an error in my math, suggestions on how to make this more efficient (obviously clearing out caves in the chunks and lighting the surface around my slime farm, but that's fairly time consuming as well), or any other ideas for how to farm slimes. Because I don't want to feel like I've wasted all this time to build something that's there just because someone else built one.
"Now when I tell you to ascend to a higher plane of consciousness, you say HOW HIGH SIR?" --Bucky Katt
Rather than funneling all the slimes to a single grinder (which takes a while and gives them an opportunity to despawn) ideally you would kill them quickly after they spawn by having multiple distributed grinders and then funnel the slimeballs to a single collection point. Slimeballs, like all items, also despawn, but it's after a fixed five minute period rather than randomly.
What senses do we lack that we cannot see and cannot hear another world all around us? -Dune