Feliway stress-reducer use in cats? Will I have to use it forever to keep beneficial effects?

It could go either way. I have 4 cats, and one of them is very aggressive. We used Feliaway, and it worked great. We stopped using it, and he is slightly more aggressive now, but not like he was. Are you using the outlet one or the spray? What I have done, is stopped using the outlet ones, and use the spray when I see him acting up again. I just spray it in his 'haunts' and that's it. Seems to help! Good luck!