Is Apple Care One beneficial with existing AppleCare+ plans?

Apple Care One. I have two devices covered by Apple Care +, one finishing in 2027 and the other in 2028. I also have two other older devices covered by monthly Apple Care + charges. Is there any benefit to me starting an Apple One cover at this stage? I know I would have to pay an additional charge for the 4th device, but unless I get a "refund" of some sort on the two newer devices which have a long-term cover I can't see the benefit. I am open to persuasion as I can see the benefit of just one monthly charge! Many thanks in advance