Although I haven't yet bought the PR7 comment - I'm still keen to do this if the circumstances are right.
So can you confirm the type of comments page that the PR7 link will be on.
Latest Comments First
1. I've seen many comment pages that list the Latest Comments First AND only allow for say 10 comments per page. So once another 10 comments are placed on the page AFTER your comment, your comment then moves on the next page - which has a reduced PR. And this process continues after every lot of 10 comments. This type of blog comment has a PR7 for potentially only a few hours (or even minutes).
2. Obviously the blog might allow for 40, 50 or more comments, but if the latest comments are placed at the top of the page (as opposed to the bottom) - then after some time your comment moves to another page with less PR.
Oldest Comments First
3. The better blog pages are those that have the oldest comments listed first and yours initially placed at the bottom. Then when some others add their comments they are placed after yours.
4. The best scenario is when these blog pages also have reasonable limits on the number of comments per page (say 10 or 20). So that after some time, the page that your comment is on is effectively fixed and any further comments go onto the next page in the list. Thus preserving the maximum amount of PR juice for your comment's link.
Tks.