After the Level Ticket exchange concluded early this year, I began sending all my Tickets to a backup user account. After every Ticket was finally backed up, I began flipping the tickets in an attempt to acquire as many standard cars I could at zero mileage.
The reason -- simply because I prefer to have all my new cars in "undriven" status. I know it's unrealistic to have a "used" car with no mileage, but you could understand I enjoy doing this for statistical/historic purposes. The point is that I like looking at a car's profile page and knowing that all that mileage is my own.
Having the Tickets intact on both my main account and backup account, I began flipping the tickets on my main account first. I replaced several current standard cars with the same ones I obtained at zero mileage. Once all those Tickets exhausted, I began flipping my other account's tickets (of course, ensuring that the game save was backed up first). Once all those cars are copied over to my main account, I restore the other account's backup and do it all again. At the same time, I always check the Online Dealership for cars I don't have in zero mileage.
The caveat, of course, is to not make this project seem like too much work. But I have taken this as a fun little side venture in addition to the usual GT5 activities -- customizing and tuning my cars, keeping up on the Seasonal events, maintaining my $20 million balance...and most of all, making it fun!