how often to oil the main spring?

[old fart]

i have a ruger lcr revolver, i wipe it down each day after i am through carrying it. i have oiled the mainspring a couple times in two years, it seems fine and rust free but dry each time i have done it. should i oil it more often?, less? i don't want to take the grip off any more than necessary, i use mobile one and barricade as my oil. thanks