Changing a user's expiration date

OK, I've searched for this and found some references to editing files with myphpadmin - however - that will take forever and prone to major mistakes.

So I'm hoping someone has a solution. I have 180+ members to add manually, enter their subscriptions and give an expiration date that matches their current membership start date.

This post may just be another +1 on the idea of letting expiration dates be modified. At this point it will take a year for all my members to expire on their normal month, be manually notified and then re-register with the subscription.