Is the prayer of one who suffers from constant flatulence permissible, and does he combine prayers out of necessity, knowing that his ablution becomes invalid between the two prayers?

The person afflicted with سلس ( سلس البول / سلس الريح - chronic incontinence of urine/gas) should perform ablution after the time for prayer begins, and can pray with that ablution as many obligatory and supererogatory prayers as he wishes until that time expires. According to the Maliki school, he is not required to perform ablution for his permanent impurity. It is permissible to combine two prayers due to the excuse of سلس according to the Hanbali school, and there is no blame on whoever adopts their view.