When should I leave day job to pursue startup full-time?

If your business progress is going well enough right now I would continue working long hours (2 jobs) until the income from the start-up makes it possible for you to leave work. It doesn't have to 100% replace your fulltime pay initially, but enough for you to survive on and be confident you can work on your startup until it really breaks through.

Keep your job for as long as you can - or until you get a client or sell something that puts you in a position to work full time at the startup with confidence.

In my experience I needed a defined runway before I made any progress. It was only when I quit my job and went full time that I actually started making steps towards being profitable. While I was working, I had too much safety net and didn't make the big steps I needed to. My focus also wasn't in the right place as getting profitable wasn't my #1 priority, it was building the software. Once I had quit then getting profitable was #1 priority and that's where your focus really needs to be.

If you have 6 - 8 months runway and you think you can get profitable enough in that time frame then I say go for it. As long as you are prepared to lose that runway money, as that's what you are risking.

Down the track I can't imagine you would regret giving it a shot, but there is a decent chance you would regret not doing so.

One last point as you mentioned raising funds, if you are reliant on this, it means there is an outside source that you are dependent on which obviously adds an extra risk (ie. if you can't get funding). If you must get funding then I would suggest starting that process right away.

If you have a sales ready product then it would depend on how long you believe the sales cycle is and how many you believe you can sell in the next 4 - 6 months. The sales cycle is particularly relevant because it appears that you are focused towards the more enterprise side (massive companies) which tend towards more hand holding and longer decision times. If you will have a sales stream before the 6-8 months of savings runs out then get out there and sell it. If it's still in development / key features are still missing, then I would stick by the day job until it is sales ready. Nothing will make you succeed like the absolute need to succeed.

There is no precise answer. You'll basically hear any of the following:

1. When your startup generates sufficient profits
2. When you become/feel fully committed to your startup
3. When your job becomes unbearable
4. When your spouse, family and/or friends are ready/willing/able to support you
5. When you've saved up enough money to work on your startup 100% for 6+ months

Ultimately...there never is a right time to quit your job and dedicate yourself to your startup. The proper advice would be to pay attention to your level of devotion towards your startup. The grass is always greener on the other side and thus, many people who once enjoyed working on their sideprojects (so as to avoid doing their jobs in the first place) find themselves bored once they've quit their jobs.

Dedicate as much free time as you can and see if really fires you up.

Whilst I personally tend to agree with Ryan, it's hard to know what's best for you and it depends on your particular circumstances and there must be lots of factors that only you are fully aware of.

I thought I should drop a quick note since I just answered a somewhat similar question. No point copy&pasting, so please take a look at my answer and hope it might help you with the decision-making process.