Is it okay to wear the same Invisalign tray for two months?

It is best to change your invisalign tray in a timely manner to stay on track in progressing with aligning the teeth. This way you can see your results faster. The more aligners your wear longer then advised the more you delay your final outcome. The effect of the aligner is complete in two weeks.  Wearing it longer then that may help retain the position but wearing it for too long may cause the aligner to breakdown as they are meant to be changed every two weeks.      

Wearing the aligners more than instructed time will delay your treatment. It won't cause any damage & but it's like a pause on your treatment. If for some unexpected incidents, you can not go to your dentist on time or there is an issue with your treatment & your other trays are being remade, wearing the same tray is ok. it'll be like a retainer, will keep your teeth from moving till next tray is ready. It's definitely better than not wearing any trays!