Scawen,
your biggest mistake - and you know that very well - isn't your announcement of new features or content, it's most probably your perfectionism.
Whole games, some of which have been fairly successful worldwide, were developed in less than two years. You guys have not given LFS serious UPDATES in more than two years.
Of course, LFS isn't your average game and you guys aren't average developers. Your team is veeeery small, so naturally your development cycles are longer. Plus, you're not depending on the services of any publishing company either, so that makes you independent from any commitments (except for the money you need for living).
Thing is, people are used to getting updates and content upgrades for games in months rather than years. You have not been able to believably communicate the obviously huge efforts you're putting in to further enhance LFS with new content and features. So people are wondering if you're really concentrating on LFS at all, if you've lost the love for it or have moved on to something else. You can't really blame them for it. They're used to getting fed more information than you're giving them, and more things to play with.
Another problem I'm seeing is that a physics upgrade, some new track and one new car won't be the "BIG ONE" upgrade everybody is hoping for, after more than two years of development. Of course most people don't know what's going on under the hood. So the things you're working on actually might technically be a major leap forward, but don't feel like that, because the difference pre and after can't be recognized by the average player.
I can imagine it is a frustrating experience dealing with a rather impatient crowd of players, but maybe you could satisfy many hungry minds with smaller more frequent updates. I've even heard that just giving people a minor new version with very few changes (if any at all!) does have some kind of placebo effect - they're feeling there's something done about the game so they're satisfied and stick with LFS. A new tire rim design here, a small dashboard update there, things that don't take months to complete but still have the desired effect of keeping players interested.
Anyway. I've been stuck with LFS almost since its inception, I'm not gonna go away (also thanks to CityLifeCrew.net). I'm not particularly interested in the Scirocco, but I am looking forward to the enhanced physics model around tires. Even if it's not PERFECT (hint, hint).
So keep it up: LFS is - arguably - one of the best things you've done in your life so far, making thousands of people happy every day.
Cheers
Gooney