Well, the problem with werecritters isn't that it fluctuates the ages (in fact, where the ages go tends to give a fairly good indication of how the world is going - a rush straight ot the golden age means that all the civs got pretty lucky, and are expanding, but that such a thing means you'll probably get a lot of trade routes, which will lag your worldgen) but that werecritters are a
major source of bloat in worldgen.
One werecritter goes on a rampage and infects a victim into being another werecritter.
Two werecritters go on a rampage and infect two more victims into being more werecritters.
Four werecritters go on a rampage and infect four more...
Each werecritter can go on a rampage two or three times a year. Each rampage involves individual rolls for the werewolf attacking people and creatures - almost all of which involve citizens running away, and maybe, at most, a chicken getting eaten.
Werecritter attacks can add
several million events to worldgen. I had a single town get attacked 10,000 times in a 350-year worldgen, after not being attacked at all for the first 80 years, and with an escalating number of werehedgehog rampages (apparently, they were Sonic fans...) reaching over 100 rampages per year for the past dozen or so years. (And the population of the town was still in the thousands, and the livestock still existed, so these were pretty darn ineffectual rampages.)
It's a
problem Toady needs to address. Turning off werebeasts
results in much faster worldgen.