Everything 1.5 is keeping offline volumes in my index

[void]

To have Everything automatically remove old or offline volumes from your index:

• In Everything, from the Tools menu, click Options.
• Click the NTFS tab on the left.
• Check Automatically remove offline volumes.
• Click OK.

To manually remove an offline volume:

• In Everything, from the Tools menu, click Options.
• Click the NTFS tab on the left.
• Select an offline volume.
• Click Remove.
• Click OK.

[raccoon]

To show only online volumes in search results without removing offline volumes...
include the verb online: into your search query.

@void: Suggestion. For user convenience, could you add a menu item under the View or Search or Index menus, [x] Include Offline Volumes enabled by default, or [ ] Exclude Offline Volumes disabled by default? I'll leave it to you where this option belongs, but I suspect the Index menu. Might even join the "Result Omissions" section.