Let me start by saying I have been playing FM games since before the days of Sensible Soccer on the Amiga!
I've noticed when reviewing attribute declines of older players that physical attributes decline extremley quickly in their 30s - almost rapidly between in mid 30s, this doesn't seem to be influenced enough by natural fitness. For examply my world class goalkeeper is 3 agility at age 40, my target forward's strength declines to 8 etc. Acceleration, Page and also appear to decline too rapidly over a short number of years in early 30s. This seems unrealistic to me - I doubt a non league goalkeeper would have a greated agility than a word class former Brazil number 1, even at age 40. I feel the decline on physical attributes in general is too steap, although this is just my opinion, as a 40 year old myself! The below player had double physical training throughout his career.