This question may seem obvious, But I understand that the yeast does most of the cleaning up in beers and meads. So, If I was to sorbate or pasteurize, my mead, would I gain in benefit from ageing?
Obvious ? No. I have no idea what you're actually alluding to, from the point of making, especially to the "cleaning up" thing ?
The yeast is responsible for the reaction of fermentation. The fine yeast sediment then flocculates out to the bottom of the fermenter, that's generally just gravity but sometimes it needs a little help with beer/wine finings as natural clearing can take a while.
The type of yeast chosen will vary the finished ferment as to whats left, flavour-wise and how that will actually change with time.
Pasteurisation? No. It's not jams/jellies or dairy products here. It's alcoholic beverages, which once made, are heat sensitive and easily damaged.
Some think of the process as some sort of magic bullet. It's not. If you heat a batch you can drive off the alcohol, you can change the taste of a batch and yes it will kill off any yeast cells present. If the batch is going to end up carbonated, how in hells name is pasteurisation gonna help ? As you will have killed off the very material that would produce the CO2 necessary for bottle priming and would have to use either methode champenoise or forced carbonation.
Perhaps the OP could expand on what was meant ?
After all, ageing is ageing. So far I don't know of any quick way round that.......