Having done the same with a year's worth of runway in hand, I would suggest either keep your role and experiment slowly to validate your approach and idea or to maybe work out a lesser workload model if your org allows to give you more time on building your project (can come with some pay cuts, but you're still in healthy position)
As entrepreneurs, there is a big tendency to get obsessed with the solution rather than the problem when you jump in without any back up or thoughtfulness.
This in turn leads to frustrations when your approach or say model doesn't really take up or shows the same promise. And when that happens, time surprisingly just flies out! Can say this with personal experience
A more plausible route should be to keep a steady income for sometime, despite the runway because you can't predict any future problems or issues that may arise ( faced health issues myself, which did tumble my runway)
Keeping a steady will give you the opportunity to pump in your income to your experiments, building your network and connections and also give you some breathing room to accommodate your lifestyle when you eventually take the plunge with some sort of market fitment.
Definitely time consuming but then again if you are serious, will lead to more long term benefit and will keep you better prepped when you decide to start-up full time.
Hope this helps
