I should probably track down some of the blades I bought from McMaster Carr. They do last a long time. The trick to cutoff blade life is to keep the blade moving in the cut. Plunging in will just wipe out any blade quite quickly. I have thought about doubling up the Chinese blades. They seem to be okay other than their thickness.

mcmaster doesn't have brand names. I think this gets you to the blades I had https://www.mcmaster.com/catalog/125/2467
link isn't specific enough, item #1257A85 1 1/2" .049 thick aluminum oxide fiberglass reinforced metal cutoff blade for miniature dremel

$1.50 apiece is not bad for the life I got out of them