asomething that you probably already know but i don't know if your applying it to your post
-your clutch does not wear when it is pushed all the way in and all the way out.
that means you can rev as high as you want as long as your clutch is compressed all the way and it won't add any extra wear. BUT, when you do slip your clutch, the higher your rpms are the more it will wear (do a 6 rpm launch and you'll smell your stock clutch easy, do a 3 or 4 rpm launch and your ok).
so, as long as your clutched was pressed in all the way, you can run it at 3rpms for 20 secs or more (although i really don't see the need to hold it that long, but you can do it if you want) and your clutch will be fine until you start slipping it