Greetings Champions!
Hello David, my company that I work for has/had several Ebay accounts for different websites and one thing I always noticed is that when we linked our site, or the corresponding product in the listing it would hold power when searching for it. In other words Some of my listing that I put up that really never sold, I would make sure they were heavily optimized and would usually show up in search results. I also noticed that our on site sales would increase when I did this because customers would view our website after looking at the listing which lead to more browsing/buying. But as you said they dissapear after 90 days, and the selling items go away rather fast so it does become somewhat null in purpose. So it comes to a personal choice good sir, good luck on your quest for Page 1!
Justin Smith