[TYPO3-english] $TYPO3_CONF_VARS["FE"][" lifetime"] problem

[Vahan Amirbekyan]

Dear All,
I found that changing value of $TYPO3_CONF_VARS["FE"][" lifetime"]  does not 
take any affect.
I am using core v4.1.1, sr_feuser_register v2.5.7 and newloginbox v.3.0.1
I checked cookies and see that expiration date for fe_typo_session cookie 
correspondes to my settings for lifetime but still after quite short time 
( probably about 1 hour ) logging is lost. Seems like the code that checks 
client cookies is buggy. Isn't it part of the core?
what can be the problem?