I think a family subscription is a good idea but I can see where it could get complicated for the GS Accounting department. There needs to be a way to connect the two or more memberships - perhaps through a common email.
The annual premium membership is $30, add a "partner" membership for $25 and any further memberships (presumably kids, but this could be a team or a cub scout group, etc) for $20. When it comes time for renewal, there would need to be a page where you choose the members you want to renew. This is just in case someone in the family decides they don't want to cache anymore.
In the meantime, there is a quick and easy way to keep track of your and your boyfriend's individual cache counts. Buy yourself a pair of geocoins or travel bugs and "visit" your trackable into every cache you do. This will record your own personal caching experiences as well as mileage (if you are looking for a little friendly competition in that area). You can even go back and "visit" caches you've already been to.
Hope that helps!
Edited to add that I just realized you were asking about non-PMs logging premium caches, not about sharing a Premium account. But I'll le my answer stand in case it is useful to others.
This post has been edited by 6NoisyHikers: 30 April 2012 - 09:00 AM