Proper Training??

I don´t think that it is a rule, it´s more an advice, because there is a lot to learn on this field. For example in Carlos Coste variable ballast record, a 10 minutes surface interval will fit the 2:1 recommendation. But it will be safe to do another 135 meters inmersion, or 2 or 3?. I don´t think so.
I think is quite difficult to know, when the Oxigen stores are full again. And it depends on depht and time. And O2 depletion isn´t too bad either, in fact a training strategy is to work with O2 depletion.
On the other side, BO is not only due to low oxygen. It´s mainly due to low brain perfusion that also depends on vasoconstriction.

SpearoPimp,
Also do some searches at
http://www.hawaiiskindiver.net/store/board.php
Many of the successful pros train very hard, often in pools.

Well as far as I am concerned, I do all the breathing, dive, come up, let myself hypervent to go back to normal oxygen levels, relax, do all the breathing and off I go again.

As long as you feel relaxed then I recon it should be ok, make sure you get your baloon with you, I use it to rest after each dive, plus it's a good way to let other know there's a diver around (and speedboat's can't come near you either).

I do advise you tho to go to a freediving school, even if you are good at diving with no teaching per se, you do need to know how to be safe whilst diving, do's and don'ts.

lungfish - that's a crazy story ! 67m // 220 ft to get a weightbelt - but I guess that's the kind of depths that come easyto him now.

Spearopimp - I think that 45secs on the surface is about half what you need.
I seem to remember somone like efattah (maybe, maybe not - do a search) stating that 1:30 (one min and a half) was the bare minimum of surface time that you needed betwen dives. This is to clear gases and so on.
Personally I find that while spearfishing (normally aspetto) two minutes rest just breathing normally followed by a minute or more proper breathe up feels 'right'. I dont dive deep (4m to 14m - typically around 8m) nor especially long (1:30 to 2:30) but I find that without this 3min or more breathe up on the surface the dive is not 'right'....
Find a way that suits you but look intothe minimum surface time that is recommended.

Like I say I think it is 1:30 minimum...so be careful with 45secs.

Hope that helps
Ed

my deco docs recommended 10 minute intervals between any dives below 30m and 5 minutes otherwise, wouldn't want to go with much less than that - both from a deco sickness point of view but also to recover O2

S