Valet parking shops are one of my favorites! Up in West LA you can drive around for hours and hours looking for parking plus I have serious parallel parking issues.
If nothing else having a well-loved vehicle may reveal things about the valet parking that a new car would not. The shops I've done don't want your car parked on the ramp because it skews the retrieval time.
I have always been reimbursed the entire amount I paid to park. My max was $30.00.
I usually stay an hour and I NEVER ask for free parking, but if they ask why such a short visit I say something like my Tinder date must have checked me out and left, I got the wrong location of the hotel branch, my dad's flight was delayed and he couldn't reach me, the potential client didn't show, my sitter called and I need to get home and sometimes I'm not charged or they validate my parking without purchase. (I include this in my evaluation because employee compassion is valuable.)
The only thing I don't like is that the standard valet tip in Los Angeles is $5 and they only reimburse $2. I'm so uncomfortable handing them only $2, I eat the extra $3.
Have fun!!