Well to my way of thinking the rolling tier is one of the few benefits hhonors has over SPG.In SPG I have to do the stays every year,not so in Hilton.
my scenario-enough stays in Sept,october 2007 to qualify diamond so this year would only have to have one stay in early august to trigger the rolling tier and be qualified until october 2009.So enough stays for diamond in 2007 and 2009 but only one stay in 2008 would keep my status.Sounds OK to me.