Steam-boiler sight-glass leaks and gasket replacement choices

[JimNY]

Thinking of a DIY replace of a leaking sight-glass in a gas-fired steam-heat boiler.

Since it has always wound up leaking again not long after professional repair, my main question: is there any advantage to replacing the rubber ones with the more-expensive-than-rubber gaskets I see out there - teflon, neoprene, viton, etc? I mean if they can be substituted directly, will they last longer?

Thanks for any info.