Now, if you really wanted to get anal about upgrading, you could make sure all your "mission critical" apps had been updated for, and are compatible with Lollipop. The major problem with any Android update is that once you jump in, you can't go back. So, if everything works well and you're happy, you pat yourself on the back. But, if something goes awry, you'll be kicking yourself in the arse until handset upgrade time.