B2B startup: time to quit?

It seems the answer is in your question. You don't feel passionate by your startup, you are balancing it with a well-paid corporate job, and think about getting as much money as possible, as fast as possible, to retire as young as possible. In this situation, there is only one answer: do what it takes to sell your startup as soon as possible, as the highest possible valuation. Then take a good job, or try another startup idea.

My first reactions:

sounds like breaking even or paying yourself a small salary at $450k. Could you do without 1-2 of those employees? Or at least contract offshore? Remember as a niche application you DON'T need to provide "fanatical support" or have every integration; changing your outlook to this would help in framing reduced headcount + development.
how do you view your strengths in sales and marketing? $450k might be conservative if you had the right resources working for you. Hire a professional SEO firm; spend money on off shore SDRs and lead gen. If the market is growing maybe you can hit $1.5mm which is much different
what is your current run rate? How much have you spent on development? Given your post, you might be best served just cashing out today.

How can you gauge things like this ? Wasn't Mark offered nearly a billion in late 05' for F.B. . ? You never can predict the market. You might get offered 800 mil to sell in 3 years.

I ha e 2 companies one that pays the bills the other is a b2b SaaS with 2500 mrr.

I realized about 6 months ago that the niche is too tight and it will never be the thing that makes me an extra 50k a month.

Dev costs were just my time I am the technical cofounder. My partner had the idea and contacts for out first dozen customers.

Its an even split. Since it doesn't touch the revenue of my other company I spend as little time as I can on it. We have hirered a commission only sales person and are shifting down a gear in terms of our involvement.

So if it ain't cutting it either pivot or change your personal focus. 18k to 450k is a large gap.

What does the scenario look like in 7 years? I run a enterprise SaaS - here's our experience - take from it what you will.

Year 1 - 20 K ARR

Year 2 - 250 K ARR

Year 3 - 350 K ARR

Year 4 - 400 K ARR

Year 5 - 950 K ARR

Year 6 - 1400 K ARR

Year 7 - 2500 K ARR projected

Enterprise SaaS takes a long time (imho) to get traction. But when it does - it does. Your business model and feature set will evolve during the 'slow growth'. Believe it or not - that's a blessing. It allowed us to really build something our clients need (i.e. we only built what they asked us for) and then that service is worth a serious premium, as of course, no real competition exists for it - or if it did - the switching costs are extremely high.

I started the company at 32 - and left a great corporate job to do so - so I kind of understand the age consideration and your dillema.

I personally think 450K ARR is nothing to sneeze at. If you can do that and stick with it - your co will be worth enough for it to be worth your risk in 10 years.