Whether its your forever violin, a student violin destined for a younger sibling, a violin you are handing over the fence to another family starting their musical journey or want to get a good price for it on facebook ..chances are your violin needs some love after all its hard work from practice, the school journey and maybe being left on the back seat one too many times.
Strings generally need changing every year, though can last longer if you are not fussy about the tone. I generally service student violins for ~$50 + the cost of strings, this can get them sounding as good (or better) than the day they left the shop. I can also let you know if you have any problems coming up or need attending to straightaway (bridge warping, cracks , seams opening up). A stitch in time saves nine!
For smaller size instruments, and with beginner students in mind, strings are around $25, these are a quality steel core string (Clarendon silver) that are long lasting and the tone is ok on a shorter instrument (as the tension is lower). (See my Violin String Selection Guide )
For full size (and the better 3/4 instruments) I usuall fit Thomastik Alphayue, Pirastro Tonica or Thomastik Dominant depending on player level, the instrument and what you want to achieve sound wise. If this sounds like musician speak then the $50 Alphas are probably the goto string for you.
Sometimes a chinrest change, shoulder pad is useful too …especially with growing bodies and changing neck lengths. You might need a new tail piece, peg replacement, some seams have opened up or some chips need attention too.