I'm not quite sure about texts; that's a good question. I don't think that's written anywhere. I think they just sit in limbo until they're delivered, but there could be a time limit. Maybe ask a tech support rep when you call in?
As for voicemail, they're not stored on the phone, they're stored in your voicemail box, which you can actually check from another number too. I believe they're stored for 7 or 10 days.