If you have a doc library template, and you've created some doc library instances based off this template, is it safe to remove this template once you're done with it?
migrated from stackoverflow.com Oct 27 '11 at 2:06
Libraries created from a template are not tied to the template, so the template can be removed if it is no longer required. The same holds true for Site Templates.
Yes, the template can be removed.
I don't think it's a good practice to remove any components from SharePoint, unless you've removed all provisioned instanced of this component in your case list instances. You can always change your List template and set Hidden attribute to TRUE so it won't appear in the UI.
If you meant list definition, the answer is NO.
We had a real situation at work, when deletion of a list definition which was previously deployed through a feature, broke the list instances which were created based on the definition.
In our particular situation, deletion of list definition produced exception 'Invalid file name' (0x81020030) on page load, when it was trying to access the collection of list views (in SPRequestInternalClass.GetViewsSchemaXml method).
The list definition was created as a List Definition project item in Visual Studio (with Schema.xml).
The screenshot of the error from the corresponding bug report:
You can check out the full-sized screenshot.
Eventually, I haven't found any resolution or workaround on this issue, and we had to restore the removed definitions.
So, even if it is not always true, you'd better check somewhere on staging environment :)