Its never a good Idea to have the lid completly off. Taking off the snorkel does wonders. or take the snorkel off, cut a hole in the top of the Lid, and EHS racing sells a kit that has an outerwear and cool looking mounting bracket/allen head bolts.
Yea and I use to also. But like I said its never a good Idea. I didnt say its a bad idea, just not good.
You could ride for years and never have a problem, but then one day something gets inside your airbox, past your filter (if not on correctly or cleaned correctly) and into your carb, mixed with gas/oil/air and sent into your cylender. Yea might not happen, but you never know.
If your going to run it with the lid completly off, Id suggest getting the proper outterwear for the filter your using.
also the conditions you ride in would equate wether or not its a good idea to have it off. ex. Mud/water/heavy dust or sand. Sand is a sneaky guy he gets everywhere.