I've installed iOS 8.1.1 on my iPhone 6 Plus 128GB and it has NOT cured this problem. Had previously found by trial and error that it seems definitely to be an issue with the number of apps installed rather than the amount of memory used - or its a combination of the number of apps and the overall memory used for their storage.
Can install up to about 940 apps with the phone still staying reasonably stable. I had also after this added about 30GB of music and still no problem after several days. So then added about 3GB of podcasts and still no problem.
So yesterday, upgraded to 8.1.1 and after backing up (probably a waste of time), the phone has again been mostly trouble free today. So added about 20 apps later today and the crashes and self reboots started all over again...
Seems to me it's certain Apple know about this problem but either can't or won't fix it. I raised the issue through Apples online chat (BEFORE 8.1.1 became available) telling them about my experience only to be told they wanted me to speak to one of their senior advisors. The senior advisor joined the chat only to immediately wipe (for me at least) the previous on screen conversation. The chat then went dead - so I had to start a new session (because they wanted no evidence of my chat that I could screen snap?). On the new chat, I was asked if I would mind the senior advisor phoning me.
Agreed to this and he rang me about 25 mins later. One of the first things I asked, was had he heard of the issue. He claimed he hadn't (first lie). I explained to him what I'd tried and how the problem seemed to be related to the number of apps installed. He made no comment except to suggest that I try again to reinstall all my apps one at a time and not restore from a backup.
This annoyed me because all he was suggesting was something I'd told him I'd already tried several times. After some heated discussion that got around again to me trying to get him to admit he knew or Apple must know about this problem, he then claimed Apple had never heard of the problem either (lie 2)!
So, I asked him, how did he go from telling me that he had never heard of the problem, to then telling me that Apple had never heard of the problem - weren't the two positions contradictory? His reply to this was to claim that he knew everything that Apple knew.
I then became very angry and we then spent the next couple of minutes trying to shout each other down before I gave up and put the phone down. He did not ring back.
All this suggests to me that Apples senior advisors have been told to deny their knowledge of this problem - lie in other words. And I say lie because of what others have said in this post about their experiences. Although I have thought of repeating the process (chat followed by phone call) to see if I get the same denial from another advisor.
So what to do? Following choices I'm considering -
1. Like others have said, adapt to the issue and restrict no of apps installed
2. Try and cancel contract on phone and return it - suspect this could be difficult
3. Try and swap the phone - although this sounds likely to be a waste of time
4. Consider legal action against Apple - suspect again this would be very difficult
I've been an Apple iPhone and iPad user for several years now but am very seriously considering moving over to Android. It isn't just this iPhone issue either. For years iTunes and its so called backups have been hopelessly unreliable and I've had enough.
But is Android any more reliable than Apple? So many more different phones and a less secure OS suggests it probably isn't!