This depends on where you live and whether or not hummingbirds migrate or live there year round.
In general, follow these recommendations from Beilke for when to put hummer feeders back up:
Midwest and Northeast: Put your feeder back out in mid-April, which is the earliest Ruby-throated hummingbirds begin to arrive in the spring.
Mid-Atlantic: Have your hummingbird feeder ready by early April.
Southeast and Gulf Coast: Put feeders up by end of February. But hummers also may winter in places such as south Florida or along the coast, so you can leave feeders up throughout the winter.
Pacific Northwest: Get your hummingbird feeder ready by February for early migrating Rufous Hummingbirds.
Some states, such as California, Arizona, Oregon, Texas, parts of Washington, and southern New Mexico have various hummingbird species year-round.
This means you can leave your feeders up throughout the year in these places.