I work in an environment where computer security is a very serious subject, and I have an almost paranoid level of OCD when it comes to online security -- but an expiring password on a "*#!&" communications account, are you freaking kidding me?!
We have too many personal passwords for too many things that require so many variations that the only way a person can keep track is to have another password on a password manager. The *last* thing we need is one of our service providers (that has very little potential for financial or reputation damage on my part) thinking they know better than I do whether my password needs to be changed.
If you want to support expiring passwords, *offer it as a configurable option*! But please don't assume you know better than I do whether my password needs to be changed, and force expired passwords on us according to your definition.
This is frustrating when more than one person (i.e. a spouse!) is accessing the account.