The weak market conditions that prompted Canfor's announcement this week of production curtailments at its B.C. and Alberta sawmills will last until about midway through next year, two forest industry watchers are predicting.  By then, price of western spruce, pine or fir two-by-fours should have bounced back to the break-even point.  Some analysts estimate that level to be between US$500-$550 per thousand board feet, well above the current level of US$365.  Starting December 19, curtailments lasting from one to four weeks will be invoked. In a ...