Staying with a feeling too long

When do you know how to stay with a feeling and for how long? Yes it is a vibration in your body. I get a feeling of deep sadness (grief) and stay with the feeling and the action of crying. What if this crying goes on for quite a while. How long is too long to cry? Does it depend on what you are processing and when might it be self indulging? How do you determine this? Is it possible that I am being self-indulgent with crying when I start getting obsessive thoughts or some other “cue?”