Norton is such a resource hog too, or at least is was in the past. Haven't messed with it for year. I personally use AVG on PC. Like others, I don't really worry about anything on my phone. I've tried some here and there over the years, but as long as you're smart about where you download things from and etc, I don't see a need for it on the phone.
The exploits that we hear about sometimes, AV isn't going to protect you from most of those, so it's really only necessary if you're downloading apps and things from shady sources, in which case, better advice would be to stop doing that than to install AV software.