When router drops out do any of the lights on the front change colour? Possibly going to orange on dsl or broadband.
Does your landline still work when drop out happens?
If you have a spare filter, change the filter and just double check wiring.
This will eliminate it being a wiring / line issue.
Google "what's my ip" and make a note of your ip address. Switch router off overnight, or longer if possible, when you reconnect check ip address again and hopefully you will have got a different one.
If dropouts still occurring try a hard reset of the router - usually via a small hole, using toothpick or similar.
If still dropping out - suggest fault on router - contact netgear.