Topic approved.

A Foam filter start to deteriorate based on the material it is made of, from 2yrs on.ie., the cheaper aftermarket one made of poor quality foam will not only loose it's ability to filter (pores become larger)but also deteriorate ,become brittle and come off in small bits. The paper filters last much longer if kept sealed ,as much as 10 years or may be more.
The other most consumed and often used material is the Engine oil. Most Mineral oils if kept sealed can continue to have it's original properties till about 4~5 years...after which the additives breakdown and oil cannot be used. As a thumb rule any oil older than 2~3 yrs is a risk to use.
Batteries start to deteriorate after 6 months of storage , so while buying a Battery it is best to buy one which is 2 months or less old , as increasing months of storage will lead to sulphating.
Petrol kept in storage without exposure to Air will last upto 30 to 45 days.
Hope this helps.

Absolutely useful info, thank you very much. I believe the Gixxer filters are paper filters. On second examination, when I said sealed, I might have been a bit wrong about that. The plastic cover that it comes in has got a hole or two in some of the pieces, so they probably have been in exposure to ambient conditions. Not gonna take risk with that!

Thanks once again!