Restoration increases value for certain pieces today. What types and will this last?

[perezfan]

A lot depends on the level of degradation to the piece. In some cases, restoration would hurt the value, and in others, it helps.

Take Stadium seats for example... If the chair is thrashed, with flaking paint, loose parts, rust or wood rot, then restoration is probably advised.

If the seat simply has paint wear or more minor flaws, then restoration wouldn't be warranted. Most collectors prefer these things in the original state. So changing away from the original version should always be done as a final resort (IMHO).
It just depends upon the level of severity.

Hartland and Bobblehead collectors frown upon it and for most collectors,
any type of restoration is a deal-killer. Same for vintage Pennants. My gut feeling is that it's more acceptable with paper items, due to the fragility and greater potential for degradation, discoloring, tears, etc.

Just my .02... Also, you might get a better answer if you can state the specific type of sports collectibles you have in mind.