Offer an ad free paid level for users that don't like ads.
And a premium level ad free with extras/more data/tips for users that want more.
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I like the ability of having a tiered approach for pricing... I don't think I would ever completely remove the free tier, as my data is incredibly helpful to a lot of people so want to still offer a value resource to all.
Just some better/more advanced stuff for the others that would like more...
Removing ads as a tier is a good idea as well.
I like using the auto-responder emails to push the subscriptions and affiliate links...
Seems to work pretty well.