No one knows for sure until we actually go and just the scenario of biological recycling of conciousness obviously won’t leave any memories and account for deja vu at the very least.Unless recycling of conciousness only takes place among the same species and even then doubtful as conciousness and memory is realistically linked to the previous dead brain if we’re staying with just biological factors and science.Although some clues might exist in the ongoing scientific research into documented out of body experiences of those on the margins of death before being saved by successful CPR.
However might as well throw the Church’s view of what happens to us when we go into the possibilities in the form of the ‘soul’ and the tricks which Satan is said to use to fool the unwary in that regard.Which leaves the question how do we know if it’s God helping us to get to his realm,or Satan tricking us with false hallucinations into his.The hard drug induced end and effectively telling the afflicted to give up on their life,enforced by the Palliative/Hospice regime on its unfortunate victims,rather than fighting illness,prolonging life with treatment and hoping for a miracle to the very end,obviously helping the latter in that regard.