Re: limited life of flash memory: yes, flash memory does have a lifespan. But, something else will cause one to get rid of their device before the flash memory dies. Flash today is pretty hardy.
Case in point: I used a day-one iPad 3 for six years without any storage issues. I got rid of that iPad due to no software updates, frequent "page was reloaded" messages in Safari, battery seeing better days, and sloooow processor. My Macbook has a 6yo SSD that's still running strong.
But that said, I would agree to a "more is better" approach as today, a 32GB iPad might suffice, but one might start to add more apps, more OS bloat, more pictures/videos/audio, spreadsheets, magazines, etc. So if have the cash, better to future proof. And if you are selling an old device, that will cover the cost of the upgrade.