How should I account for membership dues?

[Buddha Buck]

I am keeping the books for a new not-for-profit and need to know the best
way to track members and their dues.

We encourage members to commit to an annual membership, but allow them to
pay either all at once or monthly (e.g., an annual membership costs $600,
and we'll either take a single $600 payment or 12 $50 payments).  For other
purposes, we need to recognize the income monthly.

In GnuCash, I have tried creating an invoice for each membership, but with
12 line-items, each dated a month a part, and then applying payments to the
invoice as a whole.  This doesn't work because the invoice gets posted to a
single date, and has a single due date.  The income isn't spread out across
the year.

I have also tried creating a dozen invoices, each dated a month apart, and
then applying payments to those invoices.  Without scheduled invoices (on
the GnuCash WishList since 2003, I believe) this is a real pain.  But it
seems to work.  This has the conceptual problem that I would like the whole
membership to be in a single "lot", but currently there is no way to
control what invoices and payments go into a single lot.

Is there a better way?

Also, for the pre-payments, is it better to create a Liabilities:Prepaid
Memberships account, and on a monthly basis book a payment from that
account?  Or should I just allow Assets:Accounts Payable have a negative
balance (at least, for that member) until all 12 months are invoiced?

Thanks for any advice.