Hi Renee, Yes, LD means Limited Distance, which is usually 25 or 30 miles. It doesn't become endurance, according to AERC rules, until you ride 50 miles or more.
For some of us, 30 miles does require some enduring, however. I usually refer to my horse as a distance horse rather than an endurance horse because of that technicality. I think that as you suggest, many if not all, of the folks who ride gaited horses in endurance switch gaits. I don't really think you could or should expect a horse to rack for 30 miles, although that is Hunter's gait of choice. I would guess that in a 25 mile ride, he might rack for 10 or 12 miles and that would be interspersed with (blasphemy) trotting, flat walk, some RW, and maybe a little cantering. Toward the end of the season, he was flying along at a speed rack on a flat stretch near the finish and the two women riding behind me (MFT and Arab) told me they had to canter to keep him in sight. The gal on the MFT tried several times to buy him. I didn't think she'd really want to deal with some his less than sterling qualities. He and I have sort of learned to like each other. I don't want him to have to start over again. Nancy