I would not count on being released from a DH on the last day. That's only if you've already been on duty or will be at the end of DH for 9 hrs. I have never been released from a DH while on reserve. I've even had a scheduler tell me we don't release DHs. It might work out in your favor but often by the time 9 hrs is up on a PM schedule it's way into th night and they're aren't any options to commute home.
Commuting in to begin a PM reserve is easy.