Right. When they do do their jobs, they are pretty objective, more than say your tenure review committee
For instance, patents have no value, unless they are highly prized. But the fresh PhD syndrome indicates that more often than not, CIS does fall for fluff and packaging. And attorneys are needlessly pusillanimous about EA and OPR, if not thoroughly inept.
I was somewhat similar to you, no real rush, 3 years left on the inital H1, but I started with GC stuff within a few months of H1. I don't really have a home country to go back to... and was bugged by having floated around the US for ages before, hence the rush. I also wanted the freedom to devote time to my first interests- in the arts. The inadequacy of the system here is that it restricts you to a single "in demand" career choice, making you a highly qualified robot. Versatility is stifled. I wonder how much the US and the world has lost because of this limitation. I, for example, could never finish two books I started writing a long time ago.
I could have filed even sooner, but, for a year, after needlessly filing a Labor Certification, I just did stuff I liked and let the momentum build; excepting secreting one or two really strong pieces of evidence. So, when it was time to build a case, I was done within a couple of weeks. That no one else is doing exactly one type of research I do, was both a disadvantage and an advantage, and I of course took full toll of the fact.
I agree that cover letters don't need a prescribed length. It needs to be long, if your case "needs to be puffed up". It also needs to be long, if the evidence you provide, is not easily accessible. In my case, I had to give a lot of contextual detail as I went along, so that the letter was comprehensible. Even then, I think it was no longer than necessary and precise on the points it was making. It also made reading the actual evidence redundant. If your evidence is direct, a precise letter is the best.
On another note, I finally got my card today.
Now, I am off to do very "apple pie" things- find a job delivering pizza, and buy an Uzi. Science and Art be damned! Would you like extra cheese on it?