Rubbers have a certain life time which depends mainly on the usage and care of it. You should change your rubber on these occassions:
a) Whenever you feel that you can improve your technical skills with another rubber: This uses to happen after playing for certain time with the same rubbers, improving your skills and needing either the same rubber with different sponge thickness or a totally new and different rubber with similar characteristics to your current game.ç
b) Whenever you are not happy with your current rubbers: This happens when the rubber properties do not match with your playing characteristics.
c) Because the rubber has lost its initial properties: It becomes normal that after playing for more than 50-60 hours with a rubber it loses some of the original properties. This period of time could be shortened when using optimizers. If you normally train twice a week we recommend you to change your rubber two times a year. The best timing depends on everyone's calendar but we recommend to do it before the starting of the season and also during one of the season breaks.
One recommendation, if you regularly clean your rubber with cleaning foam or spray you will increase the duration of your rubbers.
You can always trust on www.tenismesa.es experts if you need any advice and/or suggestion.
Original texts from D.M.V. Sports Madison - www.tenismesa.es