So after receiving Kathryn's passport, I had to deal with the fact that it will expire, and that I have to remember to renew the passport when it does. I believe that software definitely has a half-life, so I had to question the use of Google calendar, which for our family is at calendar.lerch.org through the Google apps for your domain service.
While I like the service, will it still be what I'm using when my passport expires in 2014? What's the alternative reminder system (on or offline) that I can expect to be using at that time? In the end I decided that if not using Google calendar I would be migrating the data to whatever would be in use at that time. Since reminders work via SMS, I'm also assuming that the reminder system migrates to whatever is in use.
I guess the fall back is to just check the passports before travel, but the general issue still exists. Given the transient nature of systems (software or process), what assumptions can you make to ensure that you get when you expect in 1 year, 5 years, or 10 years?