Working with small size developer teams, made me realize that there is nothing better than being a happy customer of small companies that create the product they believe in AND really listen to your and other customers' feedback. It's the fundament of capitalism I believe in.
That said, to be on topic, I have to say that I'm with LFS since early pre S1 demos (which were absolutely ahead of their time back then and had a lot of charm), but I'm completely disappointed with the current development time. It’s so slow, that I managed to grow up in the meantime.
I think that all your CUSTOMERS here appreciate that you went against the flow and decided to devote the few last years of your life to create 2/3 of the most outstanding sim ever, but arguments with the number of programmers that do not have influence on project's time and quality is a complete BS. Sorry. It's what proper project management is for - set small goals for team members along with deadlines and be consistent in achieving them. And there's a myriad of tools to help you with keeping the project on the right track.
I've been a part of several software and web development projects for the past few years and I've seen too many programmers that were too proud to say that they do not know how to do this or that and wasted a lot of precious time to learn something that could be done way faster by somebody more experienced in some specific field... or at least by someone whose time is cheaper then theirs. This applies especially to the outside freelancers that didn't have tight deadlines, so they spent a lot of time on research and were really angry if someone pointed that they do not produce, although it also took some new team members a lot of time to realize that other people on the team are trustworthy too.
Sure that LFS is complicated and I can bet that you think that you're the only person that understands the code, but asking someone to take care of some less important parts doesn't require this person to be as talented as you. It's like with Pareto's principle - 20% of your effort accounts of 80% of value, which in dev's language means do what's important and polish the details later.
You're in a really comfortable position of having a great piece of WORKING code that some niche customers love because it provides an outstanding value to them. If I were you, I'd work on licensing that to other companies to help funding the further development of the engine, maybe by creating a Forza/GT4 killer on top of LFS engine (all sim racers wet dream).
The other option I see is to ask your team members to prepare another, less demanding game using your code - maybe something devoted to rally cross, which you really don't seem to treat in LFS with as much respect as it deserves (it's fun and doesn't require 1337 asphalt skillz) or maybe something WRC related (there's only RBR which is really interesting), although this will require funds and a great dose of marketing skills, to help it be profitable.
The community might call me a troll, a blasphemer or judging by the number of posts below my nick – even a n00b, I don't care since I don't have time to play LFS and it won't really hurt me. All I want to say is - Keep LFS as your favorite firstborn child, but recognize the value of your talent and what you already achieved and make it work for you.
And to be honest - even though people in my part of europe earn on average a couple times less than in other countries, I really wouldn't mind to buy 2-3 games with the LFS' feeling a year instead of paying 1/3rd for one LFS every 2 years. And I don't think I'm alone on that.
I don't wont to be an ungrateful [beep], but all of the acutes (central european) characters are wrong. I see that Misko already mentioned ć as an example of that. The issue is that the that acute is wrong.