How important are the phases of the moon and planetary hours in sympathetic magick?
Sympathetic magick is not generally tied to astrology as the whole premise behind sympathetic magick is to use objects or actions resembling, or symbolically representing, the person or event you want to influence.
The classic example is the stereotypical “voodoo” doll. The figure is linked to the target and then whatever action is performed on it, is symbolically performed on the target.
You can always tie any intention to moon phases or planetary hours if you want to, but they are not mandatory, or required.
They can greatly empower magick by themselves, but they alone don’t make or break a ritual, as I explain more here:
I have found that every ritual I have looked at that appeared to fail was done at particularly astrologically unfavorable times, and others find the same to be true (Keep in mind, I had done these rituals without the necessary knowledge of astrology). Similarly, you will find that nearly every action, every endeavor you started that failed was done at an astrologically unfavorable time, and nearly every endeavor that succeeded was done at an astrologically fortunate time. Magick is part of all actions that can be taken.
As Hermes Trismegistus says, “As Above, So Below”. This material world is a mirror of the spiritual world above.
However, it takes great labour, knowledge, and perserverence to learn these things, so following the planetary hours, the phase of the moon, and sign she is in (which the Lamegeton gives electional rules for) will have to suffice.
I have intention to make a Saturn talisman to cure for my caries in teeth. I use the 7 archangel talisman I purchased as object and write my petition on paper with the color of black now here in the waxing moon. Black is the color of Saturn.
If you are making a planetary talisman, then yes, the planetary hours would help empower it.
In a way that I don’t have to charge it daily as I have to with the crystals?
You don’t usually have to charge a talisman daily. A talisman will generally fulfill its job until it discharges the energy it is infused with, and if it is for a long term result, then you can charge it again. A good, basic schedule is about once a month or so.
So, for example, if you charge it on a full moon, then you can recharge it at the next full moon, and so on.