This is one of the better "document maintenance" tips I've come across: Keep a copy of your health care instructions (a.k.a. advanced medical directives, health care proxy) on your smart phone and have your health care agent do the same.
The health care document (a standard item in the estate planning "package") is what I would call an "emergency document" meaning that there may be a sudden and immediate need to use the document at any given time. However, it's hard to have your original health care instructions on-hand at all times. That's why having a PDF of the document on your smart phone can come in handy!
I can't quote a particular study, but I can state with confidence that a steadily growing number of my clients (of ALL ages, by the way) carry smartphones with them just about everywhere they go. This means that they have the ability to carry a copy of their advanced medical directives with them everywhere they go.
Please note that it's always better to have an original health care document on-hand. That's because many doctors and hospitals get nervous when relying on something other than an original document. But it's certainly better to have a PDF of the document on your phone than nothing at all.
DISCLAIMER: This blog does not offer legal advice, nor does it create an attorney-client relationship. If you need legal advice, consult with a lawyer instead of a blog.