@VINODGOWDA20 said:

Does the perpetual licence mean I can use all 8 included plugins indefinitely without any annual renewal or additional licence fees?
NO annual or renewal fee.

Are future updates to these plugins included in the purchase, or would major updates require an additional payment?
The license includes any potential future updates whether minor or major.

Can the 3 seats be activated on 3 different computers, and can I release a seat from an old computer and activate it on a new one later?
A seat corresponds to a computer. You can manage the seats online., remove it from one computer and use it on another one.

If I reinstall SketchUp or change my computer, can I reuse the purchased licence file to activate the plugins again?
The license is independent of the Sketchup version. So, a license is valid as a single seat for all Sketchup versions, if you have several installed on the computer. Furthermore, if you install or reinstall Sketchup (or if you upgrade a plugin), you do not have to reactivate the license

Does the 3-seat licence have any restrictions on how the seats can be used or transferred between computers?
NO restriction. Remember that for activation and seat release you need to be connected to the Internet, because this is managed by the Sketchucation site. Otherwise, you can work offline.