I'm really not interested in fighting with you, so i'll speak in general to anyone who actually wants to read someone else's suggestion for what they are. Hopefully they aren't so elitist when considering someone else's opinion, or at least aren't interested in whether it's 100% to their liking:
I'm sorry that I offended you, I'm not looking to fight with you either. I believe you are making a simple math mistake that is leading you and people who read your post to incorrect conclusions, and that convincing you that I am right is still fully possible and in the best interest of everyone involved. Making this math mistake is common and has no bearing on who you are as a person. Please humor me and try to see where I am coming from.
The reason why i suggest value is moot at a given point, whether it be 0 or some random value, is because i assume one thing between the 27 year old in my example and the 32-33 year old. Regardless of how useful they are after 32-33, if they were the same skill-set at the time of acquisition then when they hit decline most of the time they'll be in the same sort of value range. Therefore, it's not that i discount the fact that a player might not be capable of helping ones team. That is more of a call that you the manager can take. You know how much better that guy is than the minimum required to start for you more than i do.
Just because they end at the same value does not mean it affects both players the same. The fact that you own one player for longer changes everything because the net cost
per year is what is important. Consider these two ways to evaluate this player:
Player A: 27 years old, worth 450k, will sell for 125k right after he turns 33.
Player B: 31 years old, worth 225k, will sell for 125k right after he turns 33.
Using your method:
A: 450k/6 years = 75k per year
B: 250k/2 years = 113k per year
Using alternate method:
A: (450 - 125)/6 = 54k per year
B: (225 - 125)/2 = 50k per year
Using your method A is clearly better, while using the alternate method B is clearly better (considering experience and the time value of money).