Warehouse lenders that finance nonbank mortgage firms continue to report strong commitment volumes and usage rates, but there is an underlying fear that the good times won’t last forever. Nevertheless, that’s not stopping their telephones from ringing. “We’re seeing more requests for increases in lines than decreases,” said a senior manager who spoke under the condition his name not be used. “Most of our lines are holding steady.” Bob Garrett, executive vice president of mortgage warehouse lending at First Tennessee Bank, said...[Includes one data chart]