More Awesome Than You!

Right. Dead sims must retain their files, since they're still referred to in memory and ancestry....usually. It's possible for a dead sim to become completely "disconnected", but the game doesn't detect this case, and so you never lose files: If a sim were to be dead and deleted (no tombstone), everyone who knew him were to also be dead and deleted, and everyone who had ever HEARD of him was dead and deleted, this would mean that sim was completely orphaned and could be cleaned. But the game doesn't scan for this case, and it's somewhat gruelling to do so manually, especially since the dead can be talked about for generations to come.

Right.

Not entirely true. The Critical Fixes existing can keep a neighborhood chugging for quite a good while longer, but obviously, this doesn't account for any undiscovered bugs, or any new bugs of this nature (too many iterations is generally most visible sign) introduced in future expansions. If Maxis never wises up, this is going to require future critical fixes.

Early errors begin to set in around 800-ish. All known problems of this nature are resolved by Critical Fixes. Advanced errors can set in around 1000+. These are also resolved by Critical Fix hacks. Obviously, once you have to resort to hacks just to keep going, you've crossed the Rubicon already. How long you can keep going after that depends on how long it takes you to be assassinated. This point is unknown.

Unknown. This should not be occurring under any normal or abnormal in-game condition. This sounds more like failure to commit file changes to disk, which is a more serious problem. Causes include "locked files" due to being open in SimPE or "dead" instances of TS2 (even if they appears closed, they may not have terminated cleanly: Check your ALT-CRTL-DEL).

Correct. Attached subneighborhoods share their populations with "main" neighborhoods, but not lots. No doubt Maxis will love to flood your neighborhood with yet more garbage sims, as well as new NPCs.

Pretty much. Once you've passed the Critical Fix point, you're doomed. However, this point is very far away, as Critical Fixes have been able to repair neighborhoods in the 2000s. This is all assuming you're salvaging NATURAL populations, and not garbage bloat. Let us figure, as a reasonable number, you have approximately 40 families. That's about how many are in my neighborhood right now, although some are "crunchy" and will eventually be compacted together (college students, soon-to-die relatives living in small houses with no burial grounds, immortals, etc.). If your neighborhood is bloated because of *GARBAGE*, you're best off starting over.

In theory, a meticulously maintained neighborhood can avoid a potential explosion on these grounds for the duration of TS2, assuming critical fixes are made for any such problem.

Correct. However, the actual number of files needed to bring about irrevocable collapse is unknown. Unfortunately, each new expansion pack brings about more potential sources of error. As the hackers familiar with this particular class of problem tend to keep meticulously clean neighborhoods as a result, these errors will be slow to be identified.

If you consider "32767" or "65535" as a limit, yes. Instance numbers are 16-bit variables. It is unknown whether they are signed or not, but both of these numbers are fairly large. My neighborhood has been played now for what will soon be a year, and I'm around the 500 mark. Calculating that maybe 300-450 of these files are NPCs, built-in ancestors, and other such, and it has taken this long to generate 50-200 sims naturally, (if not less - I know everyone in my neighborhood by name, an impressive feat for a man my age, and I'm pretty sure there ain't that many!), you can see that it would take years and years and years to hit the hard-mathematical limit. As to what point the game will be rendered unplayable and beyond recovery of any mortal agency? Beats me. I do know that it's theoretically possible to trim a LOT of debris if the right primitives were added (NID iteration by family!). If they were to, say, create a primitive iterating first through families, then through NIDs in families, you'd have a much lower instruction count bounded not by "number of sims living and dead", but only by "number of sims living", a far smaller number bounded by the user's patience, which is typically quite small.

None of these problems were ever "fixed", merely pushed back slightly. The worst causes of damage are attempting to crudely insert or remove famblies to the sim-bin, which tends to result in damage that is incurable without both a high degree of technical ability and deep knowledge of the contents of the neighborhood. Most players don't know their neighborhoods very well.

May I have your notes on exactly what damage I will be looking for?

She knows her 'Hood intimately as she uses it as a muse for her creative writing.
I have the tech ability. May I have your notes on exactly what damage I will be looking for?