Originally Posted by justhere

I've done both of these things before.

I've kept the same car through 4 rentals using 1-2-free promo. It wasn't a one way but the rental location at the airport is a long way from where I was going and I asked when I picked it up if I could call them and have them close and open the rental agreements over the phone. Was pretty painless. Had one little glitch but they fixed it on the return.

I've also parked at National locations over a weekend when I had a 2 week rental. Just had to ask and they let me park in their employee lot.

So it is very YMMV and you'll have to ask.