Regarding the value of older posts, this is something I sometimes do...
If I find a post that I like, and it is older than 30 days, I go to the person's blog and read posts they may have from the last 30 days and possibly up vote them. In fact, if I find their newer content to be something I am on the fence about up voting, I will up vote one anyway since I wasn't able to up vote their older post.
So older posts could still draw new readers who then go on to vote for newer posts.
Yeah but wouldn't it be nicer to just vote or tip the guy for that article, instead of working around the disabled features?