We read nothing about resuscitation in the Bible. We do read about raising from the dead, but those are wonders wrought by God, not the consequence of human actions, such as resuscitation (consider: the son of the widow of Zarephath (Kings 17), the son of the Shunammite woman (2 Kings 10), the daughter of Jairus (Mark 5, Luke 8), the young man of Nain (Luke 7), Lazarus (John 11), Dorcas (Acts 9) and Eutychus (Acts 20).
In Bible times, there was a much greater realisation that life was given by God, and also taken away by Him. In our times, life and death are considered in a far more ‘technical’ light, not least through the great strides taken in medical science.
That does not mean that a realisation that God is the giver of life stands in the way of an attempt at resuscitation. Just as we may build dykes to fight a real threat of flooding, so an attempt at resuscitation may be made for people with a real chance of survival. But we must know our boundaries; we don't always have to go to the limit. After all, we cannot stop death! That is also shown by the small number of successful resuscitations.
In this respect it is far-fetched to make a claim on a ‘time of grace’. There are certainly people who have been converted after a successful resuscitation. But a resuscitation is not a means for conversion, but a means for keeping people alive. We don't need to desperately always want to extend life in order to gain as much ‘timer of grace’ as possible. That desperate struggle is in conflict with the characteristic of grace.
On the other hand, there are also people who, as Paul says so strikingly, have a desire to depart, and to be with Christ (Philippians 1:23). But Paul says that from a very specific situation of temptation. There are however more Christians who do not need to be kept alive at all costs because they live a spiritual life in expectation of the Living One. In such a situation, such a person can indicate that they do not want to be resuscitated. That is a very personal matter.