How Do you know when its time to buy a new needle

I have a shure white label that Ive had for about 2 or 3 years. It was playing a record just fine a few minutes ago i took it off the record to play another one now its nothing but static I cleaned both the needle and the record several times and even tried replaying other records before going back to the original and I have the same problem. i think it may be time to replace but I am not sure. I was hoping to get some opinions on the matter from those who may know something about it

be carefull with an old cardridge because it can damage your records
change the cardridge when you hear that the sound is not good
i use ortofon needles because of the spherical needle that are good for scratching and it wears the record less than triangular needles (especially when these are old)