It depends on your area. We live in East Texas and I would not personally let Jaxx go without it. Especially with how bad mosquitoes were last year here in TX. I know areas in Dallas sprayed for mosquitoes but we heard from friends in that area that said they were still bad even after spraying.
Fleas can cause tape worm and can just be aggravating for the dogs skin as well as they spread fast. I prefer to prevent rather then treat after the fact.
I only treated my dogs when I lived in WV during the Spring and Summer for fleas/ticks/heartworm since it got so cold there that it wasn't really an issue in the Fall and Winter. It stays so warm here in TX though that Jaxx gets treated year around here.
I have heard from friends that do not treat that they had a hard time with fleas last year but I never saw a flea on Jaxx.