Couldn't have said it better myself. The reason most seo's have to "maintain" link velocity (from my testing, there is no "minimum link velocity" required to keep a site ranked) is because most of the links that seo's build don't last more than a few months to a year. They lose their rankings either to link loss, or some penalty (avoid these 2, and your sites should rank relatively well for many years).
People like to rank with churn & burn links but it seems they don't understand what the word "burn" means
I myself don't even know what churn means, Google translate tells me "stir / shake", so that makes it shake & burn, what a weird expression, what you can shake and burn? Hmm Sambuca perhaps, although I wouldn't shake it in such small glass, especially not when it's burning, we tried that in a club already by accident. Not recommendable, whole floor on fire (
for a short while). Now the expression starts to make more sense!
But yeah link velocity is the biggest myth invented by people selling worthless links.
You know sometimes when you check the SERP's you see some stone old site from 1998 or something, that ranks for some low/medium competitive keywords at #1 or #2, and when you check his back links it turns out he has like 4-5 links pointed at the damn site, and you do everything you can and you can't even outrank him and think like what the hell is going on here, till you witness it a couple more times. That means that Google either rewards stone old sites, however if that was the case you could just buy stone old sites and get huge benefits. However that's not the case as we all bought some aged domains and although we suspect we get some benefit it's not that we rank tough shit with 4-5 links purely cause of the domain.
So in my opinion the longer you get to keep the link, the more value Google gives to it as they treat it as a REAL link or an AUTHORITY link so it only makes sense that Google treats links that exist for a very short time as a worthless or even NEGATIVE link.
You can easily test this concept btw, just buy 10 domains, and if you're short on funds just get some dropped PR1's for $10/each, place 10 links to your site, wait a couple of months to get the full value of it, then remove those links, wait for Google to recrawl and see where you end up. I bet my grandmother that you will rank lower then before you placed those links. Now place those links again and again you will rank lower then when you had these links before.
In other words, each removed link is gonna cost you, and that way your link velocity increases every single month. You can't keep up with your rankings with 100 links a month anymore, no the next month you need 120 links if you lost 100, and after that you gonna need 140 and so on. Till you reach a degree that you can't keep up anymore as you need so many new links that Google will penalize you for spamming your site.