How often has the main title changed 1 month before WrestleMania?
 

Enough for a title match at Fastlane to make sense?

Sid won the title a month before Wrestlemania 13

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Bray Wyatt and Goldberg each won their respective brand's championships on the PPVs before Mania.

wow really?

Yep. Bray won the chamber last year and Goldberg squashed Owens

i think Guerrero beating Brock was a month before right?

Yes, I believe you are correct.

Correct by 1 day.

The Main Event: February 5, 1988. Andre pins Hogan
WM 4: Mar 27, 1988

Month and few weeks.

In addition to the ones already posted:

Rock over Angle at No Way Out 2001 to set up Austin vs Rock for WM 17

Rock over Mankind in a hot potato feud to set up Austin vs Rock at WM 15

Triple H over Edge in the Chamber to set up HHH vs Orton at WM 25

Jericho over Undertaker in the Chamber to set up Jericho vs Edge AT WM 26

Batista over Cena at Chamber to set up Batista vs Cena at WM 26

Ah that was asshole Batista, my favorite run of his.

This doesn't count. The title clearly says "1 month", not "month and a few weeks". You're better than this, STD.

Yeah, 4 weeks and 3 days is the absolute longest for it to count as a month. What was STD thinking?

Crossing my fingers that the main events both change before (points at wrestlemania sign).

You don't wanna see Nakamura v Styles?

Nakamura does nothing for me, I'd rather see Reigns than Nakamura.

This also falls into the 1+ month category:
<blockquote class="embedly-card"><h4><a href="http://www.dailymotion.com/video/x4ooxcq">Raw 02-15-1999 - The Rock vs Mankind - Ladder Match for the WWF Title</a></h4><p>Main Event of Raw. The winner will face Stone Cold Steve Austin at WrestleMania! Can Mankind (champion) beat The Rock in a ladder match? Enjoy!</p></blockquote> <script async src="//cdn.embedly.com/widgets/platform.js" charset="UTF-8"></script>

Also when mentioning HHH beating Edge in the Chamber to set up Orton v. Triple H.

You forgot to mention that during the same night, Edge defeated John Cena to set up Edge, John Cena and Big Show the next month at Mania if that counts.