I have two cats; They were given Bravecto, and they are due for their next dose beginning of May. The vet charges me $72/tube, which covers ticks and fleas, and lasts 3 months. Just wondering if there is any cheaper alternatives out there, that will cover both ticks and fleas for them? I see some alternatives on amazon, but not sure which ones are good, and which ones to trust or not for protection for them.