Don't you think that skeletons could be despawned due to long transportation? Or even won't be spawned if the player is too far away from mob spawner?
Despawned? No, I had no idea...but I did think about it: what we want to do is make a mob 'grinder' and while standing there, waiting for skeletons, we can choose to stop them and kill them or to let them flow through. I now even got an idea for a counter, counting the amount if skeletons...can they despawn? Really? If so, from what distance on...? Anyone?
According to wiki "a monster spawner is only active when a player is within a radius of 16 blocks from the spawner." And about despawning: A mob that has had no player within 32 blocks of it for more than 30 seconds has a 1 in 800 chance of despawning on each game tick (1/20th of a second). Therefore, the half-life of monsters not within 32 blocks of a player is 27.73 seconds (after the initial 30 seconds have elapsed). A mob will immediately despawn if there is no player within 128 blocks of it. Note that this is a Euclidean sphere, not a cylinder from map top to bottom and not a taxicab sphere (which is more of a diamond). Example: A mob at 0/y/0 will remain at least 30 seconds (as above) if the player moves to 65/y/65 (real distance 91.9), but despawns immediately if the player moves to 91/y/91 (real distance 128.7). File:Mob spawning ranges.png - Minecraft Wiki
Thanks a lot! I already read the spawn codes so now this is very helpful! But this makes it very hard to make...hmm, thanks again!