I recently read that you shouldn't use hand quilting thread that is too old because it could break. So In order to record how old my threads are, I now put the date I buy them on the labels.
If you test the thread and it doesn't snap easily it doesn't matter how old it is. I have thread from 1978 home-ec class that is still strong, while thread I bought 10 yrs ago was tossed last week because it was weakened. If you keep the thread out of UV rays it can last decades, just like fabric does.
If you have a thread that is extremely linty due to age, mist it with water to add humidity to the thread. It really makes a huge difference. I had a cone of thread on my long arm that created a ton of lint, and it broke several times. I misted it and went on sewing. It stopped breaking and the lint was more manageable.
I hope this helps!