I don't know ... I got a couple installs with 200+ mods that work. What I end up reporting on is not game breaking issues - mostly it is just bugs and small conflicts. It is pushing 300+ that gets me in trouble. Just takes patience and steady pace.
That and being able to play with a known issue going on and not letting it bug you to the point of not being able to play at all. Many issues are not game breaking - any modded game is going to show the seams - just how much of looking behind the curtain do you want to do? The more you get into it the more the illusion is lost and what you see is the why things are showing up and not the immersion. The more advanced modders all seem to say that they don't play as much anymore and that is large part of why I never got into modding - I'd rather play.
The innovation of Oblivion mods is head and shoulders above any other set of mods for any other game I can think of. The only games that come that close are again ... by Bethesda.
Yes,
I can get a stable oblivion, but there are lot's of simple things that I have done wrong to totally mess everything up. Like setting the heap replacement in OSR (oblivion stutter remover) to 1. Which provided the best results, but also crashed at 1.8gb of ram, even with the 4gb patch. Simply switching that to a threaded heap allowed my oblivion to keep eating memory into the 4gb range before getting purged back when indoors to about 1gb. (purging the cell buffer is not recommended when you go over the max and are in an exterior (so an automated program, such as the feature in streamline, is probably best disabled if you see over 1.8gb of ram frequently) , in my opinion)
For me, since I starting using every single correct version of mods (nothing is ever outdated - every patch known to man) there are a few simple things that generally cause a crash. Messing around with memory settings in the ini, changing things drastically on the same savegame, messing mods that change the ui (for startup freezes), messing too heavily with the stutter remover heaps and sizes. And the counting game curse.
Counting Game Curse.
Which is, once my oblivion mod count starts to rise into the engine limitation range. Everything starts to take a turn. This is mostly a lot of major mods. That is. Not just little tweak mods, but the entire fcom, level lists mods, some major quest mods (hand cleaned). Which i consider essential. Then any kind of mod beyond a very specific point starts to eat away at everything like acid. Adding that unique landscapes compatibility patch reduced my framerate by 10fps? What? Ok, I will revert to my 120mod fcom install. Install that patch. No change. Ok. !79 mod install. Install patch. 10fps drop and mild stutter. There is like this certain point where oblivion starts no longer care what complexity or script intensity a mod has and just counts any additional data as overload. And you could have 300 mods (via merging) and get the same result (if they are smaller mods) , but there is only a certain amount of inner workings that can be changed before some cap gets reached. And then it all starts to crumble. And it's not linked to memory used, or cpu being eaten by script polling either. It's 100% some kind of internal overload button.
Right now I have 3 oblivion backups (120gb compressed) and i keep switching one out, testing, installing one or two random and small mods. Hits cap. Each additional mod takes a huge hit on performance. Until about 20 mods later. Crashville. The actual mods being installed don't really matter. They could be anything from a compatibility patch to overhaul mod.
So the only way for me to escape this, is to plan out exactly what's most important. And understand as best I can the point before that happens. And stick well behind it.
Then again, if you simply had a fcom+UL+BC+combat+100 or so more. That would still likely not lead to any of what I am talking about. However, the more you install mods, the more attached you get to them, so 200 mods starts to seem more like something you need, than excess.