My comments on this suggestion and suggestions of maintenance for the voting system:
I think that 3 Rounds, each a month long of collecting new stuff and pushing to get it into the top 10 of the 3 months is just fine, culminating in a 1 vote top 10 thread for two weeks or so. I recall seeing Toady One Reference this at one point to determine what we all really think are "important suggestions", as such, it shouldn't ever loose the ability of introduction of the new, or the ability to abandon the old.
I do think the top 10 list isn't a bad thing though, since there are some things I didn't vote for that I feel are as important as some of the things I did (Immigration control has been consistent for me as the 3-vote system has been there. The other 2 are generally the last frustrating things I ran into, such as designating trade zones, engraving constructions, or keeping the dwarves from assured death zones. When it gets down to it though, I don't see any problem with mass building constructions. I consistently build fortresses with 2000+ Walls, and do it just fine. Better stack handling, on the other hand, is something I would vote for if it wasn't so low on my list.)
A good example is this, what I would consider my current top 15 Suggestions
01)Forbidden area designation
02)Immigration control
03)Allow engravings on constructed walls
04)Complete overhaul of job system
05)Better Economy
06)Trade Designation (Both d(t} and k{t})
07)Combine stacks / better stack handling
08)Stop dwarven entrance dance when ordered inside
09)Door access lists
10)Transport vehicles + better hauling
11)Filter for construction material selections
12)Material selection for materials used in workshops
13)More Uses for Fat
14)Resizeable viewport
15)Show lever connections
As they shift and adjust, sometimes something becomes more important then others, sometimes new stuff comes on, or goes off. You will still notice some of the top 10 of the last thread isn't even on that list, and some are and close to the top. A top 10 allows a quick glance what the community feels is important and in what order, while 3 rounds of additions allows the community to add new stuff, and show consistency with certain lower priority items that are constantly cropping up below the top 10 threshold but still important.