I can't say precisely when this started, but I have more things to paint than time. I am fond of saying that if I quit my job and painted 10 hours a day and 5 days a week, then I would still be able to paint for 6 months and not have to buy anything new. That does not stop me from buying and trading for new things though.
I think it all started in 2008 when I started a 40k budget. I allotted $15 a week for minis. That was enough to get a blister pack (back when they were $7-$14 instead of $35) or I could save it week to week and get a bigger box.
There was always The War Store. It was great to get anything I wanted that was 40k at 20% off and cheep shipping. I saved up a few weeks of my weekly budget (or sometimes spent money that I might not have actually had)and put in a large order to Neil.
At some point I discovered Bartertown and was able to get some minis pretty cheep. I was able to get the occasional mini that I wanted for less than half but they were often assembled and painted needing rehab.
The tower above is just the NIB stuff that I have. There are things primed on sprues and in in bits that would astound and amaze. Really I should just paint what I have but that is not going to happen. I am still going to buy and trade for things. The perfect world would be to get people to trade me new minis for painted ones but that project is not going as well as expected.