This is not about depreciation cost alone.
Normally vendor tie support cycle to depreciation cycle so you cannot get new parts or support unless you pay them heavily.
Are you talking about renting gear from vendors? This seems again to be a misunderstanding, no-one is renting anything. Support contracts are normally separate, certainly they are still available at normal cost within 5 years, the normal depreciation timescale.
It seems this is a really misunderstood topic. Maybe someone can do an "understanding depreciation for startup founders" post or something.