The latter years are usually not that profitable. For the PS3 , you can see that from 2012 and 2013 the PS3 was hindered by PS4 R&D. Then in 2014 and on the PS3 wasn't all that profitable, to offset the PS4. Meanwhile the PS4 profits in 2019/ 2020 have been hindered by PS5 R&D and the latter years will look even worse.
The Wii U's latter years were straight losses to Nintendo due to them focusing on the Switch.
Depends on if you are talking about a profitable console or an unprofitable one. PS3 lost Sony a ton of money overall. But even then the later years they lost less money compared to their early years. Wii U is a similar story. Nintendo lost a bit in the early years and made a bit after.
Now look at a highly successful console, like the PS4 or Switch, then the latter years are the most profitable. A high install base translates into more software sold and more subscriptions.