Speedtest resuluts return to norma after I cycle router Off/On

then all is ok
do you have a question somewhere also ?

How long does it take to get slow again?

Once I reset it

then all is ok;

until it happens again.  

I haven't noticed a pattern, not sure there is one.  I just know that it happens; too often, sometimes more often sometimes less.

 I just   checked it and I'm getting a 14ms Ping, 3.7mbps DL and 3.9mbps UL.  
After resetting it I get                         10ms ping, 10mbps DL and 6.5mbps UL
I tried one more time and got            9ms ping,  11mbps DL and 6.7 mbps UL

o you have a question somewhere also ?

Are you asking if I've asked the question before?  I don't recall; but it's possible, I'll check my Hx

if it happens after only a few minutes, thats because cable modems jack up latency to slow down your connection to balance their network. The only way I know how to avoid that is to use a router that will speed limit you to below the givin speed.

if it takes hours or days, that could point to a problem in your router. What kind of router is it, are there firmware updates available?

I just checked it again and got 9mn 15 and 8; so it varies but it hasn't dropped back to where it was when I first checked.

Linksys WRT160N v3 router.

I rarely think about my router; and when I do, I have to break out the manuals and read up; when I can take the time...  

That will be my next step.

Thanks, I'll accept that as the answer.  

I've also contacted my ISP and was told to plug the Ethernet cable directly into my computer and do speed tests over a couple hour period; to see if they fluctuate as dramatically as they have over that past hour.

Provided resources to research the problem; as it relates to the router.

glad to help. Personally I'm fairly disappointed in manufacturer router firmware in general as they don't really care to update after the device is sold.