That's a good question. It could be a philosophical one.

Some would say that "unconditional love" is forgiving indefinitely.

Others would say that repentance is required in order to forgive, and therefore the answer to your question would be once.

Still, others, would say that the answer lies with how many degrees of forgiveness there are. For example, some may only begin to "forgive" by not wishing revenge on a person per se, but rather accountability and justice, including restorative justice - a sort of hopeful prayer that the person who did the wrong will be the one to instigate restorative justice. Then the next level of forgiveness would be to hear the person who did the wrong out, and then to sit with their answers and their asking for forgiveness a while - that is, until you are ready, or until you know that what they said was genuine. Sometimes retribution is required beforehand as well. Then the next level - regardless of whether or not the person is remorseful or not - is to forgive one small area at a time, first by reasoning with a higher power or some other philosophy about releasing the wrongs done to you to the wind, a fire, the ocean, or the earth - by some ritual that you allow to let go of the pain one small area at a time, without negating the lessons learned from that experience, and without negating that forgiveness does not mean that you're a continued doormat or that you are obligated to restore any relationships.

Forgiveness is how you define it. It's not a religious act per se, unless you want it to be.

And in some cases, some people are just not capable or ready to forgive in this lifetime. Perhaps they have cognitive delays, or perhaps they are too harmed to be able to forgive. In other cases, people may choose to never forgive, and so the answer in these instances would be zero.

Forgiveness is a great topic to address here. Some therapists will use that in therapy, but others will not. It depends on how "forgiveness" is defined.