Damn oil seal

My oil seals at the back of the 90 seem to keep going every 6 months or so. It's either the outer seal or this time it's the inner shaft seal (so oil is rather evident at the bottom of the brake drum and on the inside of the wheel).

Any ideas as to why the keep going?

I know I used some ****part seals once but since then I am pretty sure I used better quality (learnt me lesson). So again I have bought some reasonable quality parts making a point to avoid the blue bag.

Blue bag ones are fine if you get the ones with the letter G on the end of the part number
Seals fitted the right way around?

is the breather on axle blocked