Usually the spring and fall to keep up with the climate change.
She "let's me know" when it's time .
I'll be jamin' along and either my fingers start tripping up or I'll "fret out" a bend or pick up a nasty buzz.
The intonation rarely changes.
The neck is usually the only thing that needs a tweak.
Once a year it's usually good to remove all the strings, clean and polish (or dress) the frets, clean the finger board, and give a good cleaning in general. Then it's good to check all the screws, nuts and bolts for tightness, especially the tuners while they are not under tension.
Guitars that get used everyday usually are more stable than the ones that sit for weeks or months at a time......
........almost like they "respond" to the love & attention......spooky huh?