I actually very rarely make concierge requests proior to arrival, except perhaps straightforward restaurant reservations on occasion.

I tend to be a relatively low maintenance guest, and rarely go anywhere for less than a week long stay, so I am not pressed for time and often prefer making my own arrangements whenever I can. If I make requests of the concierge, it's usually just in passing in the lobby/club. I really appreciate it when they can pull off small miracles for me now and then when it matters most, but otherwise I do not make a habit of giving them laundry lists of requests.