I'm no expert by any means (hell I work on elevators for a living), and I'm trying to think this through in my head and I'm getting myself even more confused.

Is there, or has anybody encounterd a point of diminishing return as far as mega travel (30"+) suspension is concerned? Or even just your typical long travel 20-30". The pros are apparent but what are the cons if any. ( I'm assuming there would be some). Roll center, higher center of gravity.....

No expert either, I've been trying to talk my son into linking the back of his ranger, and think I finally got him! The other friends that I have, that have trucks, get that and more with there trucks. Most of them keep the ride hight lower and use more droop (or down travel) They arent using the 2/3 travel on compression and 1/3 down, like I was told is a good starting point.

mostly trucks get into the "mega travel" you speak of. The main reason buggys dont is for the rear the cvs cant take that kind of angle and the front really just doesnt need it on a lighter vehicle anyway. now like TT have 30+ in the rear and mid to high twenties in the front

One CON that comes to mind with huge amounts of suspension travel is body roll. It can be minimized with a sway bar, but not totally. Its just a trade off.

The first time I rode in a Geiser TT and prerunner on the street, I couldnt believe how much body roll there was. It felt like we were pitched easily 45 degrees to the side around a corner. Obviously the roll isnt nearly as noticeable on dirt than street, but it still exists.