Correction to what I wrote earlier. The Rizhiner Rebbe was niftas in 5611, which is 36 years after the Chozeh of Lublin. So it is a mere 168 years since the most recent of the list quoted by CS was niftar.
My apologies. Chabad chassidim will indeed praise other Rebbes even if they have passed away less than two hundred years ago.
Addendum: when I told a friend what I wrote about Lubavich only “holding of” Rebbes who are long gone, my friend corrected me. He pointed out that there are two other categories of rebbes of whom they hold:
1. Rebbes who have no continuing lineage, e.g. the Rivnitzer Rebbe zt”l. No reason not to hold of them if they can’t offer an opinion about lubavich.
2. Rebbes who have a beis midrash with no chassidim, who rely on wealthy Lubavich donors for their upkeep. They will automatically approve of anything lubavich says.