If you suspect the chance of a blowout, why wouldn't you put a blowoff tube in?
On another note, last weekend I bought an eight gallon bucket the came home and made some pumpkin ale.
Boy I was glad for the big bucket. No blowoff but the that pumpkin beer has been going like crazy since I brewed it Sunday night.
The air lock has been empty every morning and every night when I come home. When I go to bed tonight, if it's still acting active I may just put a blowoff tube in it just so I don't get anther empty airlock.