Is there a concession for someone who urinates involuntarily in their sleep, and their urine soils the bedding and carpets, given the great difficulty in cleaning them daily?

It is not obligatory to purify bedding or carpets from impurities unless one intends to pray on them. Similarly, impure sleepwear does not need to be purified except for praying in it, in which case only the impure spot needs to be washed, unless its location is unknown.