The tool for this already exists on the site.
Click on the "private messages" button under your name where it says: "Welcome, Irish Cream"
On that page - left side at the top of the column of choices, click on "Your Control Panel".
Top Center you'll see "Personal Notepad".
HUGE amount of space for storing your own personal text. "Write the review" there, in bits and pieces as you have time to do it. Then when you get about 10 minutes of time, select/copy-and-paste it into the review page.
No excuse to skimp on the details any more
REMEMBER: Flush your paste-buffer before you let anybody else near the PC. The paste buffer is normally "1 deep". Anything you cut/paste will replace whatever used to be there. So you can just "cut/paste" anything innocent to replace the review info (after you have put it into the review-form.)