Hello there

I am having alot of trouble understanding DNN and module caching - i am using 4.9,2 and have set my host performance settings  to 
module cache method - memory ;  performance -  heavy caching; 

I have an  HTML module  which has a property  Cache Time (secs) under page settings  -  I give this a value say 1200 (not sure how this relates to the host performance settings above ?? )  - anyway if i then make an change to this module content  it  is immediately available to everyone  - so wheres the caching ?

To compoud my confusion  I have a 3rd Pary module that takes an RSS feed  which does appear to be affected by the module Cache Time (secs) - but not in the way I was expecting. !!   eg I set the Cache Time value to 1200 however it fails to update after the expected time period and pick up a new feed - it seems to cache for  well several hours  at least  -  Im wondering if what it actually does is keep caching until no one requests a page for more than 1200 secs which is not much use if you get alot of traffic !!

any help unravelling the murky world of DNN caching would be much appreciated

thanks
John