Hmm, I'm no expert or anything. I own individual treasuries through Vanguard, I'm not sure how it would work with a fund. But anyways, say I buy a treasury now for $1000, and interest rates go up. I can't sell that bond for the $1000, but it's still going to be paying me the interest off the $1000. I would just buy new bonds to reallocate into my bonds %.
Of course you would say "well yea, but sell your bonds now, then buy the new ones" or whatever, but I don't think any of us can predict the future, or when the rates will rise 'enough' to get back into bonds, so I figure my strategy will work just as well as any.