I also found there is a limit to the level of detail a TSC can provide before things start disappearing. When designing a complex airport for my home town I ran into this limit somewhere north of 280 objects. So I had to keep the objects under this limit. Whether this just a finite number of objects, or is also impacted by the complexity of those objects is anyone's guess. I found that this limit only applies to a single TSC, as multiple TSC files covering neighbouring areas can comfortably exceed this limit even though all objects from both TSCs are visible at the same time.
I am just starting to integrate 3d objects into my template, so I guess I will bump into that as I get further along.
Well, in my scenery I display some 13k+ TMB objects without anyone to disappear.
Initial tests with 1 TSC file per TMB totally kill the FPS
Tests with 1 TSC calling all 13k TMB objects causes extremely long load time at startup (>10 minutes as far as I remember), but then everything is loaded, so no limit of 280 objects in my case.
Currently, I have approximately 45 TSC files, each calling approx. 300 TMB objects, which is the best compromise so far (long load times, but acceptable). Torsten is preparing something for me to go ahead with merging TMB files in order to improve performances.