[kevan]

Our feature toggles have tended to live for months to years. Sometimes the really old ones were our fault for not removing, for example we rewrote our payments UI in mid-2014 and the flag stayed around for more than a year after we were at 100%.

Other times integration with third-party tools was what held us back. We rewrote our product pages in 2013 but our recommendations vendor was scraping the old version until 2015 because no one wanted to spend the vendor hours switching it to the new version.

My favorite was our add-to-cart actions. In the old platform we ended up with about 10 different user flows after clicking the "Add to cart" button from 2013-2016. This case was driven by heavy AB testing (should we show a confirmation modal? tooltip? send them to the cart page? what about an interstitial page that shows recommended add-on products? etc). In this case we accepted the overhead of lots of feature switches because a .1% conversion bump moved the needle pretty far.

The shorter flags have lived for a couple months as we build a new feature and then test into it at small percentages to work the bugs out. Once they're in at 100% and we're confident we rip the flag out.