When I park a call after about 5 minutes it calls me back, then if I don't answer within perhaps 15 seconds it drops the call. This is both too fast for it to ring me back from a parked call in my opinion, and very bad for it to drop the call. As an example, I just lost a call to a vendor's tech support because the customer didn't let me off the phone quick enough when the parked call rang back so now I have to wait in the vendor's phone queue again to get them back.
Instead of dropping the call if I don't answer right away it should either keep ringing or go back to park and ring me again in a few minutes or something like that.
I use Avaya Cloud Office with Avaya J179 phones if that helps