I have 3.9.11 running very stable on a T2000 3.9.11+ hangs of course untill you get to the 3.15 series. Its had at least a month of uptime befoe there was a power outage (I don't have it on a UPS). 3.15 is supposed to be stable again but I haven't checked I will in the coming days. Kernels in between those releases can be booted for testing by disabling SMP at boot time as that is what is causing deadlocks. I currently have 6 days of uptime with quite alot of emerging of packages as I have been working though getting most of my packages recompiled with LTO.
I am not running Debian but rather Gentoo. I would like to see Debian keep Sparc support though and also would like to see Gentoo and Debian benefit from cooperation on such problems. The biggest issue on my wishlist is a usable build of Icedtea. I seems Debian has issues there as well. I've mostly been doing a few bug reports for gentoo helping track down why cmake was failing to build and such. -Chase Rayfield / cb88