Only you can decide. I suspect the comments you have received are not a surprise. It's something many people get to say from time to tome of some one who is leaving the stability of a good job and salary and home to travel the world.
I would say make sure that your finances are good by which I don't necessarily mean being able to fund your trip which is a given, but that your longer term financial future is secure or at least planned as short sighted schemes now that drain cash could cost you dear in future. Unless you can make your new venture pay or work along the way it is going to be a big expense and you may retain other outgoings while you are away.
You don't give the impression that you know what you want to do? Is this trip just putting off the inevitable decision that you are going to leave your current area of employment? You don't say what it is? If so I would say leave, don't take leave paid or unpaid but make a clean break, leave totally amicaby though, go travelling, maybe don't come back, but if you do return, come back fully refreshed focussing your attention in the area you want to work in or start up on your own. Leaving your job open may seem sensible but IMHO is just keeping the door on the past open which I get the impression you really want to close and open new doors instead. IMHO it's always better to make a fresh start, otherwise, you'll just end up back in the same job and just as unhappy as you are now. I don't believe that "going back in life" is beneficial have always found something else rather than go back.
But, yep as as one of life's few window's of real opportunity, if you can afford it, go for it.