Deet is a (very effective) repellent for things like flying insects, midges, mosquitoes etc. It's vapour puts them off, but it is not really an insecticide. And obviously has to be re-applied an a regular basis, as it evaporates. Preferably directly onto the skin. It will degrade all sorts of plastics, watch straps, compasses, plastic glasses and sunglasses, camera coverings, etc. Nevertheless it is essential to me in the midgeing season, or hour. I come up in awful long lived itchy lumps when they bite, which seems to be getting worse, and am a midge magnet.
I'm not sure that ticks pay much attention to it.
Permethrin in an insecticide, not exactly a repellent. You can spray it onto your clothing for that to provide a toxic barrier to them. Rovince claim that It gives ticks "hot feet" so they jump off the clothing. Failing that it will poison them after some time. It is also highly toxic to most aquatic life, insects, bees etc. As well as cats.
Rovince have come up with a way of impregnating their clothing into a long lasting wash-resistant matrix, applied to the fabrics before assembling them. Using "Coplymer technology from Utexbel" They say that:
"
The active substance permethrin is bound in a copolymer (mainly acrylate and silicone elastomer (poly siloxanes)). This combination ensures a perfect balance between the durability (wash resistance) and the bioactivity (by means of the silicone elastomers, the permethrin can gradually and durably diffuse out)."
See
Support & Info - Rovince - Teekwerende kleding for that, and lots more info.
Alternatively you can treat your own clothing with permethrin solutions such as horse sprays etc. A google of e.g. permethrin horse spray, or a trip to your local equestrian supplier may identify some possibilities. I'm sure these don't last as well, but it is quick, easy, and inexpensive to spray it on to any of your outdoor clothing periodically. I spray mine, but also try to make sure that I am completely covered by boots, ankle gaiters and trousers when walking or stalking in tick infested areas. No shorts for me.
I have no experience of Rovince clothing, but ultimately it must surely reduce in effectiveness, either by washing, or by time, as the stuff gradually evaporates.
As to the potential toxicity of permethrin to humans, well Rovince have plenty to say about that on the link that I have posted. I do not think that it is benign. I do not wear my self-treated clothing except when in the field, to minimise that sort of risk.
Neither do I think that soaking clothing in a dilute solution, spinning or letting it drip out onto the ground to dry, is a particularly good idea, particularly if your sewerage system may let it get into streams, rivers etc. but that's just my opinion. I would also suspect that rinsing after drying would be counter productive, but maybe not much different from getting soaked in the rain, or by subsequent washes.
I see that the Sawyer stuff is reckoned to be good for six washes, or six weeks. That sounds about right. Rovince do say that you should never tumble dry their clothing, I'm guessing that that might boil off the permethrin, so air drying only seems like the best policy.
Good luck