I'd add to this as well - if it is something you can't do while working, is it also something you can't do while working say 6 or 9 months out of 12 or even 2 years out of 3? There are probably a lot more options than you think to structure a career in this way.
Do you think most people could really do a 2 year on - 1 year off thing? To me that sounds great -- I can definitely save a year of expenses every 2 years... but I wonder what job prospects would be, or other adverse affects.
I know three or four people who've done this so it's a small sample and maybe they just got lucky. Generally it happened because they finally got fed up enough of the previous full time/permanent job they were in that they just left to deliberately take time out with no plan beyond that (though for one his previous employer went bankrupt leaving him out of a job). From what I've seen the initial decision to leave was far and away the hardest part.
What seems to have worked well is signing up for a contracting agency who look after the "finding work" part of the job in return for a cut of the pay and working on a series of 6-18 month fixed term contracts. This reduced the stress of finding work enormously. It also means that when you come back after a break, you're then more of a known quantity in a way you wouldn't be if you were trying to organise this all yourself.
You probably need to be at a certain point in your career (sufficiently qualified that you can slot into an existing organisation and be immediately productive) and not really care about career progression (there's no corporate ladder to climb any more so you're stuck in the middle somewhere which may bother some people). You'll also lose out on any long term compensation arrangements like stock options etc and typically that won't be fully compensated with a higher rate short term (at least from what I've seen) - it's a pure loss to you.
If you want to do it this way then the key thing is to work out which the good agencies to work for are - many are not well known even within their own specialist industry but they will have contacts at the right places in the right organisations. It's not something which works for every industry but where technical skills matter and contacts don't there are more roles like this around than you may think.
