If you are staying in a resort any distance from the airport it really is worth hiring a car rather than using a airport transfer, taxi or coach. We usually stay in Costa Teguise, for a week or so, outside the busy season. It invariably works out cheaper to hire a car for that time than to take a taxi from the airport to the Apartment and then back again at the end of the hols.
Two other cost advantages are that you can shop in the bigger supermarkets in Arrecife and avoid having other transport costs during you stay.
If you are staying somewhere where you have to leave the accommodation early in the last day, but have a flight late in the day, the car can be really useful as a way of maximising your last few hours.