I don't know if it is feasible or possible, but eclean is slower than molasses at least with the following options: eclean-dist -d -f -C -t1w If possible, let's target it in the 0.3.1 release
In the last re-write I did to eclean I was able to speed it up slightly from the original single file script. The (slow) search code is now split up into many smaller functions which make it much easier to maintain and modify. I do not think that there will be much speed improvement available due to the fact it is very IO dependent.
Profiling the eclean code shows that 90% of the time is spent in the portage.aux_get retrieving information about the packages. Since this is I/O intensive and necessary to execute properly, there isn't a lot that can be done to speed it up.