I can turn down a bargain. I mostly cured myself of acquiring more bikes by
First, volunteering at a bike co-op. All the greasy-hand, wrench-turning fun without the messy garage or involving the bike-counting spouse. When people want to give me their old bikes, I redirect them to the co-op.
Second, owning (and regularly riding) one too many vintage French bikes with French sized tubing and French threads and French rear dropouts and crumbly French plastic bits and other French oddities that defy explanation.
Finally, moving twice in the course of three years, both times living in a hotel for several months. Devoid of possessions other than my clothes and two (only two!) bikes, I found the lack of stuff incredibly liberating.
Edit: Yes, I still have four bikes and a unicycle. None are vintage; I come here and go to the co-op for that fix.