I'm trying to find out how long a Marketo tracking cookie will stay on a leads browser. Will it automatically delete after a certain period of time or will it stay until the lead clears their cookies?
On inspecting http://munchkin.marketo.net/144/munchkin.js, you will find the following variable: cookieLifeDays: 730. I assume this answers your question, though I have not personally tested it.
Thanks for letting us know. Is this number confirmed cause 730 days seems a very long period as compared to Google adwords and other platforms whose time period is around 30/60/120 days.