Firstly, don't uses LASORs as a source of legal information, its a guidance document with lots of inaccuracies. Use only the ANO contained within
CAP 393 This document is being eroded by EU Laws, but for the time being will suffice. Definitions used within the ANO are listed in Article 255. There is no definition for "current".
There have been different licences with different validation systems however; if you are studying for a JAA licence, that's all you need to be concerned about. All licence privileges are in Schedule 7 of the ANO and are worth reading.
If a licence is valid for two years then legally it can be exercised at any time within that two year period but not beyond the validity date in the Licence, The Aircraft Rating and the Medical Certificate; all 3 must be valid. Beyond that clubs will have recency requirements, but that has nothing to do with Air Law.