I have had the same problem, but think I've got it under control now.
Are you using eclipse or command line or ??
When I use the command line, I think I did "seam clean" or "seam undeploy" or maybe even "seam restart" followed by "seam explode". I probably tried all of these at one time or another never bothering to look up what each one does.
The idea is to remove the deployed war file from TWO places
1. $JBOSS_HOME/server/default/deploy
2. $PROJECT_HOME/exploded_archives
I'm pretty sure "seam undeploy" removes the 1st and "seam clean" removes the 2nd.
When I use eclipse (I use the free one), I first turn off "Project/Build Automatically"
Then when I am ready to deploy I do either Project/Build Project or Project/Build All depending on what I've changed. When I change xhtml, Build Project is sufficient. When I change java source Build All works. It's possible these do the same things and the difference is in my imagination, but some combination of this stuff will work for you.
You have to watch the output though. Occasionally the app does not get cleaned or undeployed. This would result in not seeing your change. Sometimes I shut down the server first and then rebuild/clean/deploy the project.
Hope this helps.
TDR