Asking for full long-term stability, for an operating system like Mint, is like wanting to have one's cake and eat it too.
Operating systems evolve, change, because hardware change and the OS must adapt to that, and there's no way it can keep the compatibility with every single hardware configuration that ever existed while adding the newer.
E.g. in my Lenovo B570 Mint 12 + MGSE had a couple of problems (overheating and bad wifi), but Mint 13 + Cinnamon works like a charm, absolutely perfect, not a single glitch. On the other hand, I cannot expect Mint 14, Mint 15 or 16 to do the same... I ALREADY KNOW it won't be the same, and that's ok to me.
As a Linux user I know that I have to do my part in order to erradicate the future bugs (to regain that mythical "stability") helping the developers as much as I can: reporting the bugs, getting involved in the development of the fixes, trying the proposed solutions, etc.
The only way I know to keep the complete-absolute-long-term "stability" of a system whithout having (as a user) to do your own homework, is never
update/upgrade your working OS and never
change your working hardware (ever!)... or pay somebody to do the fixing for you.