SAN FRANCISCO — 2015 is proving to be the year of the deal. The first half saw a record 31 merger-and-acquisition transactions worth more than $10 billion, according to a recent Ernst & Young report, and experts expect companies of all sizes to be active dealmakers this year.

So of course law firm M&A practices will be busy. But the superheated deal climate can put a special burden on in-house lawyers, especially at companies that aren't big enough, or active enough, to have a dedicated M&A team.

For lawyers at those companies, it means double duty.