Hi Cowboy,
It’s completely up to you, if you would like to allocate different tags to your sites to see which is performing best, then you can. But it would also work fine if you use the one tag across all of your sites.
Some of our affiliates use the different tags to track different parts of their site by naming the different tags, e.g. 32Red Home, 32Red 468×60, 32Red Review etc so they can tell which part of their site converts best.
Hope this helps, please drop us a line with any further questions.
Happy New Year!
Mark