So if I can boil this down into a nutshell, because the stream of comments is already getting too long: are we talking about "prorated vote worth" both in terms of daily velocity and age of response?
I agree with the sentiment that just because you had contributions months ago, does not mean that you're "highly valued" by the current community. You probably are, but the one does not enforce the concepts of the other.
I do like the sentiment that necrorep isn't highly important, especially as your rep increases, but I think that necrorep is important.
CW because this isn't an answer, but is a request to review the tl;dr recap
#Edit:
Adding in my suggestion, so that it floats up, now that it seems some consensus is here, so that someone else can mold it further:
I think that posts should have "prorated vote worth", because I think that it's important that they keep getting upvotes, and that they should be rewarded, but I feel it should wear down smoothly.
Maybe the max you can earn from one excellent post is 1000 rep, and the first ten are at max value, then (max-1) pts per ten, then (max-2) pts, etc, leveling out at 1 pt for the remaining upvotes.
Downvotes would still count against, so the highest possible drops to 998 max ... 996 max ... 994 max ... etc.
(using the notation of max - 1 because Q are 5, A are 10, right? :p)
We still keep the +100 rep cap per day per post, and we still keep the +200 rep cap per user per day (not counting accepts or bounties)