Russia Ukraine war, page-129107

well the difference between Afghanistan and Ukraine is Afghanistan was a matter of fighting some undersupplied Muhujidin whereas in Ukraine russia are actually fighting a regular army with modern equipment .

Russia have already taken about ten times as many casualties as in their whole time in Afghanistan .

This is a very hot war with prolonged battles instead of occasional skirmishes .
A lot less than 20 years of this very expensive would also completely bankrupt russia and leav it devoid of much vital equipment they no longer manufacture .
So no , not possible for russia and no , while it might go a while longer not that scale of time as you sugest at all .