Another way you can avoid broken levers, perches, etc is to mount some handguards. You can get ones which are basically an aluminum bar that clamps on the end of the bar and near the handlebar mounts, and you can get injection molded plastic ones that Acerbis makes that are actually very tough. Acerbis, Moose and others make them and they can do a lot more than just protect your levers. The Acerbis hand guards have an optional piece that mounts on them to keep wind off your hands, so you hands will stay a bit warmer in cool and damp conditions.
Using these, I can't see how it would be possible to break a lever. You could probably safely leave the spare levers at home if you had some strong hadguards on your bike.

I guess these are more intended for enduro bikes, and I'm not sure how feasible it would be to mount these on say, an R1150GS or an Enfield... But I've been using these for a while and would be one of the first additions to any bike I was taking off road.
http://www.acerbis.com http://www.mooseoffroad.com

On a related note, for anyone who has an enduro or dual sport bike that these will fit on, consider mounting a pair of Answer Pro-Taper handlebars. I've never bent a pair in all my years of riding, and in very rough conditions where you're stading up and over the bars, they can reduce fatigue since they will flex more than standard bars will. With a fully loaded bike, it's pretty easy to turn most stock handlebars into pretzels with even a minor fall.

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Wright Bagwell
http://fwc.webjump.com/xr650l/

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Wright Bagwell
http://www.geocities.com/wwbagwell/