Question on Tune Up Timing

https://brooksdyqi645.evercolumn.com/posts/indoor-air-quality-problems-that-point-to-ac-repair-in-north-fort-worth-and-how-comfort-experts-can-help

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