When my account is on Vacation Hold, how does that affect any books that arrive for me while I'm gone that need to be marked received? 

They are not marked received unless you do it yourself or make arrangements for someone to sign on your account and do it for you.

I travel, a lot.  If I have books on the way to my home, I mark them received the day I'm leaving.  Yes - I'm taking a chance that a book might not show up or might be RWAP.  But I'd rather do that than make the sender wait and wait and wait for their credit. 

Having your account on hold, does not affect the need to mark the books received.

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I'd probably taper my ordering off before leaving to minimize the number of books coming while gone. Maybe send a PM to any books that are out there that I will be gone X date to X date and will mark any books that arrive during that time as received as soon as I get home.

I've found that if I hold my mail at the post office, the books with DC get scanned as delivered when they are added to the hold pile.

But the delivery scan doesn't mark them received.  I think if you are just going to be gone for a week then don't worry too much about it unless you have several books that will go lost during that time.  I probably wouldn't order anything in the 2 weeks before I Ieft but you never know when a WL book will be offered and if it's a rarely posted, slow moving one you won't want to turn that down.  

Really it would depend on how long you are going to be gone.  I wouldn't mark 10 books received because you're going to be gone for a week.  If you are going to be gone for a month then the best thing to do is not to order anything for a month before hand if you can help it.  Put your WL on hold early.