I remember my Palm.

I would wake up, remove the battery cover and reset my device. I would go into email and download my mail beacuse I didn't want to wait an hour for it to check for my email. You ask why an hour? Because if you set email checking to anything less your battery would go dead in no time.

I would then read my email, write my replies, remove the battery cover and reset. Once it rebooted I would send my email.

If all went well and it didn't lock up I could actually also get calls, but I didn't bet on it.

So I guess they do have good uptime, well at least for the minute a day my device actually allowed me to use the network.