Online photo storage/sharing services are also worth considering. Combined with an app for your iPad, you can have nearly unlimited photo storage, available whenever you have an internet connection.
You'll probably still want some kind of hardware storage, for the important stuff. Sometimes online services go out of business; though they will usually supply tools to export your stuff back to hardware or another online service.
I use Flickr to some extent. There are lots of others.
Also, iOS 8 is supposed to offer nearly unlimited photo storage with your iCloud account. Whether that will incur extra storage fees is unclear (to me) at this time; but they are also making their extra iCloud storage fees much more affordable; competitive even.