I have never perceived a benefit with rehydrating dry yeast compared to just sprinking it dry onto your wort. Since it's easier to sprinkle, I just go that route. You can certainly rehydrate if you like, but I don't feel that the extra step is necessary.
As far as storage goes, just keep the packets in the fridge. I always keep a couple of packets of US-05, 34/70 and 71B (for meads and ciders) in the fridge at all times for impromptu brewdays.