I am about to purchase an Ivy Bridge cpu. But before I do I need to know if I have to purchase an aftermarket cooler along with it like everyone has had to do since the Wolfdales came out five years ago.
Is Intel still packaging their cpus with the defective securing mechanisms?
I've built computers with the Stock Intel heatsink on LGA 1155 with no problems whatsoever and they're still going strong after 8 months.
When properly installed, it takes about three years at high-ish temperature (full-load) for plastic to stretch enough to start becoming problematic. At lower temperatures, they might last a few years longer. Everyone I know who has used Intel's push-pin HSFs has started running into weird thermal problems 2-4 years after initial build (fan is spinning properly at very high speeds but core temps are still going out of control) so it seems those things are engineered for failure.
So the stock HSF is a reasonable option for the first 2-3 years at stock clocks. Beyond that, a replacement may become necessary due to retention mechanism deformation over time.
Seems you answered your own question: no, you don't need to buy a custom HSF. Not right away, at least: install the stock Intel HSF properly, then after a year or two, upgrade the PC in question and include a new heatsink.