Slow bandwidth for 1 to 2 weeks every month, anyone else?

I have owned/lived in my house for about 3 years. I have the 150mb speed and unlimited downloads internet with Cox. The first year, great speeds and no issues. These last 2 years have been a headache off and on. For about 1 to 2 weeks EVERY month the bandwidth creeps down to 1 - 10mb. Over the last 3 years I have not moved how it is set up at my house. When I first started having this problem Cox and I went through all the usual steps, Reset from my end , reset from their end, send a Tech out, replaced and upgraded modem, replaced all the house cable wiring, replaced wiring from pole connection to house. And the best that would happen is it would start to work as paid for, for about a month and then right back to acting up. Speed test would show slow speed and the jitter would be high. Other speed test would verify that. When it is slow, the signal is NEVER consistent, it will peak up to close to 190mb then down to .5mb and then back up, all in a second. At the start of the problems the techs where out here every month or so and they finally told me that the problem lies in ether one of their hubs or it's from them (Cox) changing the frequencies they are transmitting over the cable lines(supposedly to thwart cable thief) but they run into this problem with older neighborhoods and old hubs. They supposedly submitted a "field maintenance" order to have the hubs repaired down the street. I've never heard back and gave up calling it in because it would "fix" itself in a few days.

 My gripe and question to everyone is "Anyone else in Henderson NV having this issue? Or is it just on my block?" And to Cox, how come this never gets permanently fixed? When I currently call about this issue, whoever answers says they have no idea what I am talking about and it's the first time they have ever heard of something like it. I have grown sooo tired of repeating the whole story every time I would call