I was fairly flush when I first encountered PW some years ago, and I opted for lifetime membership.  Never regretted it.  Even when funds are low, now, I can look forward to quality downloads from PW. 
Over the years I've seen several other sites try a similar subscription plan - some with one artist, some with a whole squadron.  None were able to keep up the kind of output that Steve has, either in quality, quantity, variety, or duration.
In my estimation, the best deal in all "Poser-dom"