Using the Search feature from Home Screen indicates Season 1-15 of the Red Green Show still available on Roku Channel as well as as other free channels/apps. (Plex, Tubi, Redbox, and Fawesome).
Doing an internal Search from within all these channels did not produce a result for Red Green, but selecting them from the Home Screen Search did locate and successfully launch the episodes.
Locate the Red Green Show and then select "Add to Save List". Then go into "What to Watch" from home screen to access the Save List or Continue Watching. This way all available watching options will be available to you.
As to your original question, yes, all the content on these various streaming channels/apps will come and go depending on licensing agreements. They are usually available only for a limited time and sometimes either disappear completely for awhile or another channel/app picks them up. Sometimes they move to a paid subscription channel/app and become unavailable to stream for free for awhile.
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