An article in Acad. Mgt. Perspectives, Vol. 23, Nov. 2009 at 71, breaks down more than 2,000 mergers or acquisitions announced in Europe between 2001 and 2007. Among the many findings, one table shows the average number of days it took to complete a transaction, broken down by deal sizes in five ranges. The timeframes ranged from 123 days to 161 days. Other breakdowns give average days to completion by country, type of transaction, and payment method.
A legal department that retains a firm to assist it on such a transaction will be much better informed with information along these lines if it tries to fashion an incentive arrangement for the firm (See my post of Feb. 25, 2008: practice area benchmarks with 24 references.). Not all performance measures need come from law departments or law firms.