When I looked up the directions to do it. ( http://eq2.zam.com/db/quest.html?eq2quest=0d8b79a5bc6f59076a146059a3550746 ) It shows I can do it repeatedly. So I went for the colorchanging horse with the intention to get the wand the second time. However the feather didn't reappear. Then I remmebered a message saying the instance would reset in 1 day. So I've waited. The quest still hasn't come back.
If it's considered a daily quest you might find help typing /motd in game. I don't remember exactly what steps it recommends, but it supposedly has a work around to allow you to get it again.
Repeat for each year. Good news is, the petamorph wand is fully tradeable, so you can always make an alt, grind him/her to 10 quick and run the instance for the wand. Had to do that for that nifty dual wield fish, as my zerker froggie insisted on having 2.
If you read fully at the page on the link you gave, it says: Repeatable: Infinitely (21 day lockout) The lockout is what makes it once per year, since Bristlebane Day doesn't last that long in a single year.
Maybe it's just not showing up on my browser, but I don't see where it gives a lockout.Here's what the box says for me: Grants AA Category World Event Level 100 (Scales) Sharable No Difficulty Solo Repeatable Infinitely Related Zones: Enchanted Lands The Jolly Gnoggin Gnoggin's Hidden Cove Required Mobs: Pirate Captain Gnoggin Rewards:Min Coin: 57s, 32c Max Coin: 1g, 64s, 35c Choice Of:Horse of a Different Color Bristlebane Day Jester
Oh odd. It should show it next to infinitely. I did add a note about once per year to the wiki portion as well, now.