I have to say 2.619 hasn't crashed since I updated to it.
So maybe I am/was seeing something different?
2.599 would just lock up on me after a random amount of time (between a few minutes to a day or so) but would come back for a while after a reboot (pull power and replace). Both 2.586 and now 2.619 so far just sit there working nicely. The Pi mostly sits idle (it's used as an internet streaming radio) and 2.599 would sometimes crash whilst just sat there, and other times whilst playing (output just stopped and dashboard wasn't accessible via the web interface or the API).
Update: tried out 2.699 and it didn't improve things. Volumio still freezes during indexing of a large library and won't come back (see my earlier reply here for details). I'm in the process of trying totyc's solution here: mpd-being-killed-systemd-startup-t13641.html and will feedback. Issue is that indexing, waiting for the freeze and rebuilding costs a full day and isn't much fun so stay tuned. It's a little sad that the system got this bad on Raspi 1. After spending so many time with troubleshooting I'll soon toss it and get a Raspi 3 probably, hoping the problem won't persist there.
Update: Tried the mentioned solution from the other thread, to no avail. As soon as my library surpasses ~50k titles, the Pi won't startup the next boot. Lights blinking, but even after several hours it's not reachable via wired network, doesn't get an ip, no telnet possible. Always a reflash then. Aside from this dealbreaker building the library takes a whole day, so it was safe to assume the Pi 1 B+ was too weak to support the new volumio versions anymore. So I bought a Pi 3 B+ and voilà, works. Tested it for some days, everything seems fine, library gets built fast, UI is quick and responsive, rebooting without problems. Nothing in the situation has changed except the hardware.
After many months of frustration I can enjoy volumio again. It had a cost, but the price of the hardware is nothing compared to the lost time troubleshooting.
tl;dr - Newer versions of Volumio don't support Raspberry Pi 1 anymore. Save your time and buy a new one.