Membership which cost £25 a year the last time I checked used to provide a range of features beyond the free package including the ability to post high resolution images, to add entries that pre-dated your date of joining by more than 30 days and access to something called Blipfolio that allowed you to showcase your best pictures.
Most of these members benefits seem no longer to be available on the new site or, in some instances, seem to be available to everyone. We are told to expect news of new members-only benefits but no detail has yet been provided.
Lifetime membership was, I think, a one off offer as a way of raising funds for website development. It may be offered again at some point in the future but it wasn't something you could buy routinely.
I hope this is helpful.