Kubuntu 12.04 is good for five years and it has an upgrade path from 12.04
to 14.04 and then 16.04. Nothing in Linux comes close except perhaps a
rolling release and even there you may need to re-install periodically. You
need to remember that Kubuntu and Ubuntu offer two upgrade paths and you
need to be aware of the differences.

There is LTS and regular releases. LTS comes out every two years in April
and you can upgrade directly from one LTS to the next without installing
the intervening releases. Last April's release, 12.04, was LTS which stands
for long term support. LTS also means more stable because there are fewer
upgrades of kernels and packages. Regular releases come out every six
months. 12.10 is a regular release. The upgrade path for that is every six
months versus every two years. The trade off is that you get the latest and
greatest applications, but it may not be as stable. For most users the best
upgrade path is LTS because it is less hassle and most people do not need
the latest features or want to deal with possible breakage of packages.

The problem with Mint, IMO, is that it does not offer either a rolling
release or an upgrade tool. In trying to strike a balance it serves neither
user type. Instead you are stuck in time and must re-install every six
months or at the end of the support period. You can change your sources and
cross your fingers but that is for more advanced users and Mint caters
to newbies and Windows refugees. I wish Mint would stop sitting on the
fence. Their is too much indefinite about them to suit me. They cannot
decide between Cinnamon and Mate. They pretend to be for newbies, but do
not offer an easy upgrade tool. They support KDE and have a Debian edition.
You cannot try to be all things to all people. I would be happier if they
said this is what we are and delivered a good product instead of lots of
okay ones. To me it is indicative of confusion about who you want to serve
and what you want to be. I used Mint for a couple of years and have
installed their Debian edition as well. I do not dislike Mint. It just
makes me uncomfortable. I like to know that there is a plan besides trying
to beat Ubuntu in Distrowatch rankings.

You can avoid the commandline for the most part, but you certainly should
not fear it. You can Google and copy and paste commands if you do not like
to type them or your memory is bad. The commandline gives more feedback
than graphical tools and you can usually see where to go to fix things. The
best graphical package manager for all Debian based systems is Synaptic. It
provides more useful information and it gives more control.

Unity has gotten a bad rap. I say this as a KDE user for over a dozen
years. I never liked GNOME 2. It was too dumbed down for me and Unity
suffers from a similar problem. But since its inception, a year and a half
ago, Unity has improved and outstripped both GNOME shell with its
extensions or Cinnamon which is based on GS with extensions and Mate which
is based on GNOME 2. It is very configurable and you can even add a menu as
well as remove overlay scroll bars and global menu and change the the
window controls to the right side. That way you get the best of both. You
get familiar interface parts and the newest ones like Dash and HUD. The
Launcher is very configurable as well. You can drag and drop previously
fixed parts and can add mouseover functionality. There are many new scopes
and lenses, too. The problem is that older versions such as 12.04 still
lack some of this configuration.