Applying for airdrops is the best and safe way to earn ether. I earned more than 2 ether by airdrops although I'm still a newbie.
Which airdrops did you allow to earn so much Ether if I may ask? I have taken part to several airdrops myself but I didn't manage to get Ether in such amounts so far.
Airdrops will not give you so much except you just want to hold for long and you get quite lucky in the process with the increase in value. Bounties are much more better if you really want to be a part of a project. Once the bounty ends and your stakes are high in any of the activities, you can get something pretty good and dump for ETH.