Storing data with expiration date

[joques]

Hi,
I am using the memcache client for node.js to store data with a lifetime using the following syntax:

memcacheClt.set objectKey, JSON.stringify(value), callback, lifeTime

Although I get STORED as a result to the set operation, every time I try to get from the cache, it returns null. When I remove the lifeTime param everything seems to work fine. But then, the data does not expire anymore.
Does anyone have an idea how to fix this?
José