I'm not at all familiar with the dulcimer but on the guitar the wound bass strings start to suffer particularly with the build up of muck in the coils which tends to deaden the sound - if you "think" maybe you need new strings then you will most certainly notice a great difference when you put them on.

Do you use Fastfret before and after you play to clean the strings? It can slow the build up of grease and grime from your fingers and helps to keep them smooth and free running - although I have noticed a tendency to "squeak" if I use too much - my fingers that is!

When I played nylon strings after a while I'd notice the treble strings looking tagged and worn particularly on certain frequently used frets. The D string would always go first just above the 2nd fret - the wound coil would break first and occasionally leave a piece of wire buzzing on the string...

Basically - if in doubt change your strings! I enjoy new strings most after about a week of settling in. then they are great for about two to three weeks and then start to deteriorate - yes, tuning goes, and loss of clarity of tone.

...and I would highly recommend D'Addario for nylon or steel strings - they are the business...

Someone else will have to advise you regarding the dulcimer!

Chris