Love this! I have a tiered pay-by-usage plan, so I take steps to limit my data usage. I think day-to-day, Maps and Firefox are the only two things I'm likely to use without wifi - I've got wifi at work and at home, and that's where I am most of the time. I've mostly eschewed streaming services on my phone, and instead loaded music I already have as files, plus a podcast app that syncs while I sleep.

Some region-specific travel notes - in Japan, free wifi is a little less common than NA (though I think that's slowly changing). There's an app one of the telecos puts out that helps find networks - http://www.ntt-bp.net/jcfw/about/index.html - and you can also register with Softbank to get free temporary access to a number of Softbank hotspots - https://www.softbank.jp/en/mobile/special/freewifi/en/

In addition, there are usually free networks at JR stations, conbini, and international chain restaurants like Starbucks and McDonalds.