I think intention and level of power most important here if you want to use it for meditation.
I never considered timing specially with this rune, because I use it for void meditations whenever I feel need, because it helps immensely in doing void.
So I think if you confident in yourself about this you can do it whenever you want.
But if I am wrong someone please correct me.
But I never had problems in using it whenever I need, as I don’t use this rune for full magickal working, but I add it to breathing exercise for preparation before void meditation, or just after yoga session lying in shavasana for example I do 11 times, and then I can really immerse myself in void quietly effortlessly.