"peter p." wrote:

Here's my story of gutter woe. ...
...where I joined the two 10-foot lengths (a)nd ...no
matter what kinds of sealants I used, I couldn't get the joint to
stop leaking....

Any advice?

If you're going to go w/ DIY, did you use a connecting piece to join the
two pieces of gutter or simply try to lay one piece inside the other? W/
the connectors make and a good silicon caulk you should get a good joint
that will hold for years.

Alternatively, you could do like the old-timers and solder--that, of
course, means no pre-finished.

The "pro's" don't buy longer sections, they have the tooling to make
seamless guttering onsite. It shouldn't be too hard to find a tin shop
w/ the capability and have them run you a section of the proper length.

I've never used anything except either galvanized or aluminum so can't
comment on it...