Right now, inbound teleporters check every cycle for bots in the inbound directory and bring in a max of 10 bots per cycle per teleporter. I could probably save some file I/O and get some perf improvements by checking only every N cycles, but right now it's every cycle.
Inbound teleporters delete the bot file in the inbound directory after the bot has suceessfuly been introduced to the sim. Note that there is a delay between those two events so it is possible to have bot duplications if you have more than one teleporter reading from the same directory (the two inbound teleporters would have to be in different sims, either on the same machine or on different machines since VB is single threaded and thus serializes teleporters in the same sim). Both could open and read a bot file before either deletes it. In such cases I just fail the second delete attempt silently as I do several other strange file access race issues but while dups are possible, I'm almost certain it's impossible for a bot to get lost during teleportation unless DB crashes.
It's possbile to use teleporters to save off bots that never get reloaded of course - kind of a poor man's bot archive - just don't have an inbound teleporter point at that directory. But right now there isn't a way to change the inbound rate or the number brought in per cycle so what you want to do won't work at present unless you manually create and delete the inbound teleporter every so often or change it to intrasim for awhile or something like that. But having control over the inbound rate is a cool feature that could help perf too, so I will add it shortly and drop a buddy in a day or two.
You can sort of do what you want today by using two teleporter connected sims, one really big with lots of bots that runs slow and a small one that runs fast. Playing with different costs in each, maybe put a whole bunch of shapes in the big one to limit bot interactions... can result in some really different worlds...
Note that if bot files build up in the folder, the order they will be teleported in is based on the ordering of the dir command. Bots of the same species (same original bot file txt file name) from the same sim will be brought in FIFO I think, but bots from different sims or of different species names will be bunched together alphabeticaly I think.
Note also that teleporting a whole bunch of bots into a sim all at once can swamp the sim and spike CostX, giving you population explosions and discontinious cost events....