This is a nightly issue usually beginning around 6pm and lasting for a few hours. I have to reboot the router everytime. Its a model D-Link dsl-2750b. If I cant stream shows with out this dropping out all the time, Im going to have to switch to something more reliable.
There's a few factors we will want to look at here, centered around the time of day.
Do you notice your service slowing down when it is up, between the hours of 5PM and 10PM? If this is the case and you're fed off of a certain piece of equipment, it may be a capacity issue. Specifically the Catena SLC-5 DLC when overloaded sill exhibit this behavior. Litespan, Alcatel, and non-T1 fed Adtran equipment will not exhibit this issue. You can use testmy.net to run scheduled recurring speed tests to see if a pattern is seen (make sure nothing is streaming or downloading/online when doing this, please!)
Do you know of anything around you that turns on at 6PM and turns off around the time your DSL service corrects itself? There could be a source of EMI (electro-magnetic interference) showing up on the telephone line.