DSM-G600, DNS-3xx and NSA-220 Hack Forum

Hello
I tried looking in other posts regarding this problem, but couldn't find anything.
My G600 works perfectly when connected by cable.

Unfortunately, it's not located near a router anymore, so I'm forced to use the wi-fi connection.

When it's turned on, my G600 retains a stable wi-fi connection for usually 2 to 10 days. Up to 15 days, at the most. But them it seems to "disappear".
It's set with its fixed IP (no dhcp) and when this happens, it becomes not reachable, even rebooting the wi-fi router.
It's located in a position that is very difficult to reach, so every time I have to go and manually turn it off, and then on.
Which is very annoying.

I have a feeling that this might be an internal issue of the G600, but it could be also an access point related problem.
Because I used to have a Linksys WAG54GS in the past, and it was MUCH worse. Disconnection (and "disappearing" of the G600) every day or two.
Now I'm using a D-Link DSL-G624T router, and the disk is behaving better with it, but still, no more than a few days of continuous connection.
I hate the fact that I have to go get the ladder and climb in a very unconfortable location every time to reboot it.

Can it be a "advanced wireless setting" on the router side?

The default setting offered by my wireless router is as follows:
Beacon Interval :   msec, range:1~1000,default:200
DTIM Period :    range:1~25,default:2 
Hidden SSID :   NOT enabled 
Antenna transmit power :     Full (100%)
RTS Threshold :      2347
Frag Threshold :      2346
b/g Mode :     Mixed.

Do you think that, in your opinion and experience, changing these values would make the connection more stable?
After all, there's nothing near the router or the disk (yes, a cordless phone and a CRT monitor, but they are 2 meters away from the router.)
The router isn't particularly far from the disk: about 10 meters indoor, in an other room (upstairs). The signal strenght is excellent.
I don't think its about distance, because the wireless hardware of the disk seems to "crash" randomly and becoming unreachable and disappearing, even after rebooting the router.
Also, the disk AND the router are both attached to 2 UPS backup groups, so it's not about power fluctuation.

Do you know if this is a known issue, or if there's a custom firmware that solves this problem? Maybe trying a completely different firmware will do. I've been using this disk for 1 year, and I had to manually turn it on and off at least 100 times. Is there a utility that could be used to AUTOMATICALLY reboot the disk after a preset amount of time (a day or 2), MAYBE making it more stable?

thanks!!