Regarding long pasterns, my 7-yo Arab mare has quite long pasterns,
although the angle is good. It has given her an amazingly springy,
floating trot that is a dream to ride. I rode her in several LDs and
she did very well, carrying HW over rough terrain, but due to time
restrictions, she is now my husband's doted-on trail horse. At one time
she showed some slight puffiness around one front fetlock and
radiographs showed some very slight pre-arthritic changes, which I (and
vet) attributed more to carrying weight, possibly I asked too much (or
at least allowed her to give) in conditioning too soon, and to lightness
of bone and smallish feet, rather than to long pasterns.
However, I would think that what you're gaining in comfort is going to
cost you in strength and that the tendons are going to be a weak link
over the long run. Personally, I would be very concerned about a
horse's pasterns that are sinking so much as to be hitting the ground
and getting raw from it. I probably wouldn't go looking for a distance
horse with long pasterns (though better than excessively short ones),
but sometimes you have to work with what you got---in which case, I
would just keep in mind that it can take several YEARS of LSD work and
common-sense loading before tendons reach maximum strength, and don't go
asking for trouble by going too fast too soon, allowing shoeing schedule
to get behind, etc. And maybe in this case, supporting the leg with SMB
boots (within reason) might be worth considering as well.
Just my .02, of course. Your mileage may vary.
Susan Evans Garlinghouse