[TYPO3] huge cache_pages table and config.cache_period

[Bartosz Aninowski]

> My cache_pages is growing too fast - 1GB in one day.
> I've serached mailing list and found some tips
> config.cache_clearAtMidnight = 1
> config.cache_period = 3600
> I've installed cachemgm extension to monitor cached pages.
> Everythin seems to work ok, expiry time is set correctly but my 
> cache_pages table still getting biger and bigger.

Any help?
How does it work?
Does expired content remain in cache_pages and is replaced with new content 
after page hit or is deleted after expiration?
I can't figure out why my cache_pages table is getting so big.
I had to add cron script to permanently delete cache_table.