Can you elaborate on the scenario you're asking about?
HDDs don't slow down from age, rather fragmentation, and that after the outer tracks of platters are filled, more data added nearer the center at same RPM is a slower linear speed. SSDs do not have this issue.
Frame rates (assuming gaming) don't go down if the game is written properly to entirely load that section/level of the game, regardless of whether HDD or SSD.