On February 14, 2012, the Department of State published a rule that could lengthen the validity of your L-1 work visa.

The new rule would permit issuance of an L-1 visa for the period authorized by the visa reciprocity schedule rather than until the petition expiration date. For example, the visa reciprocity schedule permits holders of Indian, German, and British passports to receive five-year, multiple-entry L visas, regardless of when the L-1 petition expires.

Of course, there must always be a valid underlying L-1A or L-1B petition in place to use the L visa. In any case, L-1A and L-1B petitions are only valid for seven and five years, respectively.

Reciprocity schedules by country can be found here.