NoD - I agree, delaying the retirement age means longer time to command, and effectively it means an extra 5 years at F/O wages. If you get your first job at age 35 the extra 5 years means you are looking at a 30 year career rather than a 25 year one. Financially that that's worth about £175-200k, but the extra 5 years of pension payments will make a bigger difference.
As you say however, it's the law so arguing about it is pretty fruitless. I do believe it's a good law (for once), even though I am one of the people who will take longer to get command as a direct result.