Why Is My Buffalo Router So Slow All Of A Sudden ?

Fix Buffalo Router So Slow Speed-

I'd say that the problem is bad memory management in Buffalo router firmware. Basically whenever Buffalo router needs to have lots of connections open it uses up its RAM which is normal.

When a connection is closed that RAM should be freed up. It looks like in your case it isn't. As Buffalo router has less and less RAM available it becomes slower and slower and in the end, you have to reboot it.

When it is rebooted contents of the memory are cleared and you have fresh memory to use. If that's the case then there's very little you can do. Your router may be supported by third-party firmware like DD-WRT or OpenWRT (where's the rest of its name? I can't tell without it) so you could try installing one of then.

Otherwise you could hope for new version of official firmware that could fix the problem. I had a similar problem on a Buffalo router and solved it by getting a router that supports OpenWRT. I haven't had any problems since then.