Deon,
Here's a list of some maps I generated using default parameters and the following sizes and seeds, along with their results:
Large
1111111111 - "The Cyclopian Dimension," freezes at year 74, tried twice
1234567890 - "The Cycolpean Realm," freezes at year 50
4294967295 - "The Universe of Omens," freezes at year 71
3333333333 - "The Domain of Portents," freezes at year 26
Medium
1111111111 - "The Cyclopian Dimension," generates fine
1234567890 - "The Cyclopian Realm," freezes at year 4
4294967295 - "The Universe of Omens," generates fine
3333333333 - "The Domain of Portents," freezes at year 2
I have a dual-core 3.0 ghz Intel processor, and it doesn't matter how long I let the game run, there is no progress from these years on. Hope this helps!
[edit]
Finally got a decent-length gen with megabeasts still alive by adding 100 mountain caves and 800 other caves. I started playing Dwarf Fortress mode, and everything was going fine until the merchants arrived. The dwarf and wizard merchants headed to the depot and waited to trade with me, but the Nazgul merchants proceeded to destroy my front door, still, trade depot, carpenter's workshop, the living quarters of three dwarves, and mason's workshop before I saved and exited. Is there any way to force my 7 dwarves to attack them? I think they're just going to continue through my fortress and destroy everything now, because they supposedly departed for their journey before destroying the third living quarters and the mason's workshop (neither of which were on their way out), and they seem to be moving slowly inward. I'm enjoying the theme, but this is a bit of a gamebreaker. Did my massive number of caves create a Nazgul civilization, or were they there already?