It can get funny, as the simulacrum is not as competent as the archmage, or if someone manages to subvert the simulacrum.
Exactly half as competent. Which can be interesting if the division of knowledge skills is randomly determined. It also means that the archmage is still the only one* casting 6th-level or higher spells (they're probably not as smart as the original either). There's one choke point.
Given that simulacrum are constructs and explicitly can't advance, I'd say they have no XP and can't make magic items, so that's another choke point.
Simulacra certainly can't make more simulacrum, and each one costs the caster 1000xp minimum.
An iron golem** costs 5,600xp, 80,000 gp, and takes almost 3 months of work; a stone golem 3,400xp, 50,000gp, and nearly two months. A swift strike to take out a golem seems like a worthwhile endeavor; it takes a lot more to replace one than it does to destroy one.
These aren't unlimited resources. I don't have my books in front of me, but it looks like above 18th level, a wizard has 17,000xp per level. That's only 3 iron golems.
*I realize that archmage status in the FR doesn't apply until you're 24th level or something, and you've bonked at least three quasi-deities, but i am old and like to pretend it still begins at 18th level, with the acquisition of 9th-level spells.
**I'm picking on iron golems because they do show up in Cook's book. The Star-Rider (bad guy) has a small army of them. Unfortunately, when he's not looking, Varthlokkur sneaks in and using his Secret Weapon (a weird evil ultra-powerful fetus creature) to telekinetically pick them up and drop them from a very high height.***
*** Yes, I'm aware that iron golems weigh 5,000lbs and there are spell resistance questions. However, Radeachar (sp) is a weird ultrapowerful artifact/creature/thingum, and his primary power is telekinesis, so as DM, I'd allow some leeway. Also it's not D&D. One could also assume that Varth spent 9 weeks and a little cash to create a
lift iron golem spell. Way cheaper and faster than building an iron golem.