Three of my favourite cameras have bellows (Zeiss Ikon Nettar 515, Franka Solida III and Voigtlander Vito II) which are clearly ageing a bit. The Nettar is 75 years old and the other two 60-odd years old. Should I be doing anything to prevent the bellows cracking/splitting? Is there anything I can do? I am lucky enough to have these three in very good condition and would hate to have to replace them - I doubt paying for repairs would be economically viable.