Some good points regarding the aging of synthetic lane surfaces . Some years back, there was an article in BTM that was interesting. In that article, it stated that with the original
(first generation) Brunswick synthetic surfaces, they found that the heat created by the friction of balls actually hardened the lane surfaces to a degree due to a chemical reaction caused by the heat of friction of the lane surface. It resulted in the fusing of the surface, causing less traction in the high track areas. Since then though, as synthetics evolved, the general effects of synthetics as they age is as Avabob stated.
     

Current oils are slicker and the volumes are different.  This makes older equipment more susceptible to over/under.  When on a house wall on a GOOD surface, it would be quite noticeable.  On a worn surface, you might not see it as bad, but the new covers match up to the new oils IMO.

Yes you can use the older stuff and score BUT I think you might have more fun with a newer cover ... they are very good at controlling the rip off the dry and blending the wet/dry.

I get less over under (less hook too but its predictable) with the old stuff (PK18 and Activator especially, N'Control PB yeah over under hell with any volume) but may well be style dependent and of course not all house shots and synthetics  are the same.  First to admit on sport though probably better off with the new stuff.  Also I do love my Forest Green for the heavy stuff so new stuff has its place and have a bit of both.