No, please don't. Spider mites are usually well controlled by beneficial mites and insects. Regular pesticide use can actually encourage spider mite problems by killing off their predators. Spider mites don't pose much risk to healthy plants. If you discover damage caused by spider mites, spray the plant with water. This gets rid of most infestations.

This is true in general. Predators reproduce more slowly than prey species, otherwise they would keep killing off their food supply (this sometimes happens anyway, Tachinid flies and tent caterpillars for instance). So repeated blanket spraying causes explosions of pest species, by repeatedly taking the predators out of the equation.

There is also the problem of a percentage of the pest population surviving the pesticide doses each time, with continued spraying tending to cull out susceptible individuals and allow resistant lines to build up and become dominant.

No problems yet and ...... wondering if we should be spraying for spider mites preventatively and
regularly?

===>>> never spray preventively ... spray when you have IDd a problem ... and go from there ...

many sprays require contact ...

some of this fear could have been avoided.. had you opted for a more diverse planting ... but that is water under the bridge ...

i have struggled with juniper tip blight on Js ..... but never had a problem with spider mights on Js ... but then i never grew this cultivar ... dont know if its one of those susceptible to either ....

ken