Mine has been on my phone for a few weeks. I also take the precaution of downloading a copy to my phone in case there are problems with the app on the day. The one time I have forgotten to do this was last night in Manchester, and sure enough the bloody app wouldn't even open at 7pm, so I had a very frantic few minutes trying to find my tickets on the website. Needless to say I have made damn sure to download my York ticket.
I just want paper tickets for everything again, everything being digital is supposed to be better but it's just STRESS