You know bored employees often quit, so why aren't your pausing every once in awhile to assess your top performers' boredom levels? Sometimes your best employee leaves because he wants to move somewhere sunny or because his wife got a new gig on the other side of the country. Sometimes that uber productive engineer can’t resist the lure of her own startup or your communications ace has decided he wants to be a yoga instructor instead. When it comes to reasons like these, there’s very little you can do to keep the team you’ve sweated to put together intact. But most employees don’t leave for reasons like these. Many employees leave simply because they’re bored. And if you let them, know you could probably have prevented their aggravating departure with just a little bit of attention and care, writes Silicon Valley engineering manager and author Michael Lopp on his blog .…