Why I don't bother with replaceable phone batteries anymore

I used to buy spare batteries for my phones- right until my note 2, bit not since. I stopped using them  when I got into the habit of having to charge my smartphone every day. I was still carrying my note 2 battery around (note 2 wouldn't last me through the day). However, I didn't use it as I could plug a USB charger into a PC in the office. And then I got an s4, and then a note 3- and Samsung made previous batteries incompatible (not very pleased about that Samsung!). And then inbuilt phone batteries started getting better - the iPhone 5s gets me through a day, as does the lg g2, and the note 3 (only just, surprisingly). And now the lg flex which outlasts any other phone battery I've used before.

I also have a portable battery charger- great for taking away over weekends, several phone charges worth, with 2 USB output sockets. Making me free of having to buy spare batteries that are out of date when I get a new phone (http://www.techradar.com/news/portable-devices/other-devices/best-portable-chargers-14-we-recommend-1178873#articleContent)

Yes there is always the thought that my inbuilt phone batteries will die, but I haven't had that problem (yet)- I had an iPhone 4S which lasted over 2 years (went to my wife after a year). The battery didn't need replacing, but it was easy enough to do. I've never kept a phone for 2 years, and whether a phone has a replaceable battery age didn't make for a higher selling price so it's a mute point.

Now if only batteries would last a few weeks.