If you still qualify for a medical, why switch to an LSA?
Don't get me wrong, I fly a LSA as it meets my mission now. But at some point in the future should the family want to fly with me, I'll step up to the private pilot certificate and maybe look for an aircraft with more useful load. But for boring holes in the sky, the LSA does fine.
If you no longer feel the need to fly IFR, why not just continuing flying the aircraft you have now in VFR conditions? I don't think a specific age would dictate IFR vs VFR operation. Or perhaps I'm not understanding the question?