query plan caching (sql server)

Question

Is there a measure of time frame as to which the execution plan of inline queries will cached?

Answer 1

There is an algorithm (will find it), but practically it will stay there:

• while being used (Edit: See AdaTheDev's answer)
• until statistics update (also implied by index rebuild)
• until definition changes (including whitespace and case)
• SQL instance restart
• until severe memory pressure

SQL Server 2008 article

Answer 2

As gbn said, there is an algorithm. Just to add that the length of time a plan will be cached for also relates to how valuable a plan is deemed to be and how often it is used (if it's a higher value plan, and it keeps getting used then it's value is very high so will be more likely to be held for longer than other plans)