Finder freezing vs. USB disks on Airport Extrem / OSX 10.8.2

After having used for a long time different distant USB disks plugged on an Airport Extrem (AFP protocol with accounts ...), I conclude that in Mountain Lion, this schema induces too many issues with the Finder (Finder freezing, Finder restarting impossible, OSX unable to restart itself etc ... ).

Really only linked to ML ? Not sure either !

In fact, if i'm using simple shared folders, on the same network, with AFP protocol on an iMac (under SN 10.6.8 ... ) : I never encounter any issues !

Thus I privilege different ways to explain :

USB disks are growing old too fast, to be plugged 24/7 (in fact, they are not servers and not built for that !); just a little bit tired, they induce too slowness to be handle correctly by Finder.

Or there is a real issue in the AFP protocol between ML and the Airport Extrem shared disks.

Or it could also be a question of electrical tension on the USB port ...

It could be interesting to get the opinion of someone who uses a Time Capsule ... an hard disk built into an Airport Extrem.

In any case, from now, I will reinforce datas saved on BDs, DVDs ou CDs recordable, because, at the end, they are the ultimate solutions to preserve our memories , far from any risks of disks diseases, or erasures performed by error !