Consider that it is very expensive to repair damage to the water line once it enters the home, so it is worth the extra trouble of disconnecting and reconnecting the garden hose. In the summer when there is no danger of freezing temperatures, this is not a problem. You also asked if it was necessary to water in the fall and winter. Plants are alive even when they are dormant, just as we are alive when we sleep. Their physiological processes continue, admittedly at a reduced rate, but never the less they continue.
Water is essential for the continued health of the plant.
Because of the reduced rate of the physiological processes and because of the reduced evaporation at lower temperatures, water should be applied less frequently. During the autumn when the weather is cool, water once a week. During warm spells, you may need to water twice a week, especially if it is windy. In the late winter, often one of our very dry periods, it is important to ensure that there is moisture in the soil for trees, shrubs, perennials, and bulb plants.