Get a 70-200/4 - love it, then one day really need f2.8, feel dissatisfied, buy a 70-200/2.8. Later feel the need of IS and upgrade to the IS version.
Also get the 24-105/4 - love it, then one day really need something faster, get a 24/2.8, 50/1.4 (preferably a Zeiss), plus an 85/1.8. But keep the IS zoom.
Then one day see what an 85/1.2 can do, feel dissatisfied with the 85/1.8 and upgrade to the L version.
Also notice how abysmal the 24/2.8 is, and upgrade to the L. Then one day really need something wider than the 24/1.4 and feel dissatisfied. Look around confusedly. Test some bad Canon zoom lenses and feel dissatisfied some more. Someone shows you a Zeiss 21 and you buy it becuase it makes your work look wonderful. But feel a bit dissatisfied with the waveform distortion.
Then one day you make the mistake of trying a 135/2 and of course you have to have that.
Then one day you need something longer than the 200/2.8 IS and you buy the 300/4, but it doesn't have IS, so you upgrade to the 300/4 IS.
Then you find that you're not using the 70-200/IS much because it's so big and heavy, so you buy a 70-200/4 because it now seems so light and sharp. And you sell the Zeiss 21, too, because it's worth so much money now, and it doesn't render straight lines. And someone tells you that the 300/4 non IS is much sharper than the 300/4 and you're not sure whether to believe them, but it makes you feel slightly dissatisfied with the IS version.
Then you think: wouldn't it be great if I could sell all this junk and just buy one really great long, fast zoom lens? And you look hard at the Sigma 120-300 f2.8 and you try it but it's too heavy and that makes you feel dissatisfied.
So you look at the 100-400IS and you think: that's the answer to all my problems! But you try it and you find it's not very sharp and that makes you feel dissatisfied, so you get a Sigma 100-300m f4 and it's great! And you use it a lot but eventually it makes your arms tired and it's soft at the long end and it doesn't have IS and that makes you feel dissatisfied.
Then one day you have to do a shoot in the rain, and you worry about your 5D because it's not weatherproof (and that makes you feel dissatisfied) so you try the 1Ds II and it's GREAT. And then you find that none of your wide angle lenses are sharp in the corners and you wish you hadn't sold your Zeiss 21mm and that makes you feel dissatisfied.
So you sell everything, go on holiday, come back and buy a 350D with the 17-85IS lens and find that it does almost everything you need it to do anyway, except the viewfinder is rubblish (and guess how that makes you feel?) and it's a bit flimsy, and then you start to think the long end isnt long enough and then someone tells you that the Sigma 18-50/2.8 is a lot sharper, or the Tamron 28-75mm and you read all these posts praying for Canon to release the new lightweight full frame 17-300mm f2.8 L IS but that just makes you feel dissatisfied becuase it turns out to be just a rumour, and then you decide to take up painting.
