Im with you on the accumulation of grey hairs
My dizzy mare wont allow me to put a stick next to her, she obviously thinks its going to eat her lol, so its a bit of guess work, ie measure me and I stand next to her ha ha but the physio said she reckons shes easily 16.2 and those friends that thought she was smaller when I bought her have said omg shes grown as we are not on the same yard anymore so they havent seen her for a while. I dont think we realise seeing them everyday too. I found she chunked up a bit, then went lean, must be the growing bit, then chunked, lean and so on. I do think some horses seem to mature for longer, they reckon Draughts are still growing after 6 yr old. My friends WB is 5 now and shes praying he stops growing, was bought as a yearling to ake 16.2, hes 17.1 at her last measurement and very gangly!!