Question on Tune Up Timing

https://johnnymtqx530.meridiannest.com/posts/water-heater-repair-and-ac-repair-under-one-call-in-north-fort-worth-through-comfort-experts

Question on Tune Up Timing Does anyone know if spring or fall is better for a tune-up? Not sure when it makes the most sense for an older system in Summerfields, since the AC works hardest in summer but the furnace matters in winter