I use Revolution on sakura. I only apply it on her mosly just in the spring and fall. I started using it because she had a bad case of earmites and it worked great for it. Ive just been using it since
I treat the boys only the summer. They're both indoor kitties but my cousins cats go outside and sometimes I bring home a little unwelcome guest. But during the winter I haven't had that problem yet.
All female (males aren't bloodsuckers) mosquitoes potentially carry heartworm.
All they need do is bite an animal with heartworm and then bite another animal.
Revolution will keep the skeeters off your pet, but will also kill them if they do settle for a snack.
I think flea prevention is a good idea in the warm weather months.
What you might do is buy some and keep it on hand, then flea comb your cats once a week or so. If you find signs of fleas (flea dirt or live fleas), then you can treat right away. I do agree with being cautious about using pesticides on your cats unless it's necessary, but the products are safe and fleas can potentially transmit a variety of illnesses - from tapeworms, which are gross but relatively harmless, to hemobartonella, which can potentially be deadly.