wireless connection goes down unless I ping every 170 seconds

I am using a Linksys Wireless-G USB Network Adapter with ural.

(Hmmm... should there be a hardlink for ural.4 man page? Should ral.4 
mention "ural"?)

I have used it off and on for several months. And now for past six months 
it has been used constantly.

But this summer, I found it lost its connection frequently. Even if I had 
open ssh sessions to it (sshd has default TCPKeepAlive yes).

From some trial and error, I found if I ping at least one packet (9 bytes) 
every 170 seconds to my router (wireless gateway) my connection stays up. 
I do: ping -i 170 -s 1 192.168.1.1

I have been doing this for months and it works fine. But whenever I don't 
do that, my connection will be down within a few minutes.

This has been on three different wireless gateways. So now I am beginning 
to think the problem is local to my adapter or ural.

Has anyone heard of anything like this?

(I do have a different system that I will try with a different 
builtin wireless and also can try this USB wireless on it. But haven't got 
to that yet.)