You get a estimated delivery time during the booking process. If it wont arrive within that time (its quite long to be safe) you can contact Eurails Customer Service for a solution eg. one option as you said would be the change to a MobilePass anothen one could be  Refund + you buy it from one of the Ticket offices in Europe (Few railcompanies still sell the paperpass at their International Ticket office) 

The Passes are always send by signed post (that way both Eurail and you can monitor where the passes are). 

Thank you very much, seewulf.  Are the estimated delivery times fairly accurate?  We’re just trying to stay away from hassles (like the squirrely app) as much as we can and I read about a lot of problems on the eurail community with paper passes.  If it appears that the paper passes will not be delivered in a timely fashion (not withstanding the estimate), how far in advance of our travel date should we ask for a refund? Or does it even matter since it’s a refund and we will be buying a brand new paper pass in Europe?  I presume the cost of the pass in person (in Europe) is more in person than it is online.  Thank you again.  Very much appreciated. 

3 months is definitely fine. I would worry about 2-3 weeks but otherwise no.

You'll get a tracking number for peace of mind.

The pass is the same price in person but not all stations/countries offer paper passes. I'd order online. You might need to book seat reservations in advance too (and sometimes you need to add the pass number).

Thank you very much thibcabe.  I went through a practice booking (estimated delivery date of June 12 - I read longer average delivery time for others on community forum) and they did not specify the mode of mailing (i.e., which delivery service).  Around here, some modes of mail service (UPS) are better than others (U.S. Postal Service and Fed Ex, for example).  Would anyone happen to know which delivery service eurail uses to Maryland in the eastern United States? Also, and because eurail makes such a big deal about the value of these passes, I presume that anyone who is present at home can sign for delivery of multiple pass holders.  Please correct me if I am wrong. Thank you very much, again.  

Follow up to thibcabe - I have already started to book seat reservations on deutsche bahn (no Eurail pass number required for seat reservations on this site) in advance of Eurail pass purchase.  Thanks again. 

The passes will be sent in the name of the person ordering the passes, so that person has to sign for the delivery. 

Thanks, AnnaB.  It’s a cumbersome delivery process for sure.  Thank you again.

Once the passes have been sent from Eurail, you should monitor the delivery so that you see if the delivery gets stuck in customs. You will get a notification from EUR once the passes are sent.

Thanks again, AnnaB.  Very helpful information.  Much appreciated.