One thing common about all wood frames is that you never know what processes it has gone through such as staining, washing, etc. Most wood frames are acidic and contain sulphur which will over time change the natural state of the art work. In most cases, yellowing is most common.
Originally Posted by eggshell
Since you are framing with pt/pd, the effect of yellowing (if it happens) might look really nice and no need to worry about it.
One thing we do in conservation framing is to seal the wood frames and fillets using Lineco Frame Sealing Tape. It very easy and not expensive. The tape is aluminum and blocks out-gasing from the frame.
I am usually framing color work and conservation framing is very needed. In your case, it might be overkill.