Shelf life of oils VS time of use

[Josip]

Many oils have suggested shelf life of 6 years when they are bought new. Then again it is suggested that watches should be serviced every 6 years so.
 
My question is:
If a watch is serviced with a brand new oils...
OR
...With oils that are near their recommended shelf life
 
Could one expect there to be a significant difference in the performance of the watch? I mean, in theory, the oils are either 6 or 12 years old at the time of the next service.
 
Let’s assume that the oils have been properly stored

[canthus]

Properly stored to me means in a full (or a near full as possible) glass container (does not react with additives) with a tight lid, stored upside down (oil acts as a further seal for lid), in a warm fridge (ie not near freezing), in the dark (like the can Mb supply their oils in).  I would then be happy with 10-12 year old oil, otherwise 6 years seems fine.  Synthetic oils will keep their condition longer than ordinary mineral oils.

High levels of light, heat, air or moisture will increase oxidation and degradation.  Metal containers can 'use up' the additives for rust prevention etc.

[canthus]

I forgot to mention that my comments are for storage of oils.  The oil should be at room temp when applied to the workpiece.  If it is still cold then it will be more viscous (thicker) and will not flow as easily into the gaps etc.  However, if as most of us do, it is put into an oil pot/well then the small amount will soon warm up to room temp.

Using very cold oil on a warm part may also result in the microscopic amount of water in most oils (yes they do contain some!!) condensing out under the oil film.